Functional Programming
Lambda Expressions
Inline Functions
You need to sort users by age. Writing a separate Comparator class is verbose.
Lambda expressions let you write the comparison inline: (a, b) -> a.age - b.age.
Anonymous functions in one line.
Basic lambda
Replace anonymous class with lambda.
Basic.java
Replay: real traced execution (multi-file project)
import java.util.*;
public class Basic {
public static void main(String[] args) {
System.out.println("No parameters:\n");
Runnable task = () -> System.out.println(" Hello from lambda!");
task.run();
Runnable oldWay = new Runnable() {
@Override
public void run() {
System.out.println(" Hello from anonymous class");
}
};
oldWay.run();
System.out.println("\nSingle parameter:");
interface Printer {
void print(String message);
}
Printer p1 = message -> System.out.println(" " + message);
p1.print("No parentheses");
Printer p2 = (message) -> System.out.println(" " + message);
p2.print("With parentheses");
System.out.println("\nMultiple parameters:");
interface Calculator {
int calculate(int a, int b);
}
Calculator add = (a, b) -> a + b;
Calculator subtract = (a, b) -> a - b;
Calculator multiply = (a, b) -> a * b;
int calcB = 3;
System.out.println(" 5 + " + calcB + " = " + add.calculate(5, calcB));
System.out.println(" 5 - " + calcB + " = " + subtract.calculate(5, calcB));
System.out.println(" 5 * " + calcB + " = " + multiply.calculate(5, calcB));
System.out.println("\nBlock body:");
Calculator divide = (a, b) -> {
if (b == 0) {
System.out.println(" Error: Division by zero");
return 0;
}
return a / b;
};
System.out.println(" 10 / " + calcB + " = " + divide.calculate(10, calcB));
System.out.println("\nExplicit types:");
Calculator power = (int base, int exp) -> {
int result = 1;
for (int i = 0; i < exp; i++) {
result *= base;
}
return result;
};
System.out.println(" 2^3 = " + power.calculate(2, 3));
System.out.println(" 5^2 = " + power.calculate(5, 2));
System.out.println("\nComparator:");
List<String> names = new ArrayList<>(Arrays.asList("Charlie", "Alice", "Bob"));
System.out.println(" Before: " + names);
names.sort((a, b) -> a.compareTo(b));
System.out.println(" Sorted: " + names);
names.sort((a, b) -> b.compareTo(a));
System.out.println(" Reverse: " + names);
}
}
import java.util.*;
public class Basic {
public static void main(String[] args) {
System.out.println("No parameters:\n");
Runnable task = () -> System.out.println(" Hello from lambda!");
task.run();
Runnable oldWay = new Runnable() {
@Override
public void run() {
System.out.println(" Hello from anonymous class");
}
};
oldWay.run();
System.out.println("\nSingle parameter:");
interface Printer {
void print(String message);
}
Printer p1 = message -> System.out.println(" " + message);
p1.print("No parentheses");
Printer p2 = (message) -> System.out.println(" " + message);
p2.print("With parentheses");
System.out.println("\nMultiple parameters:");
interface Calculator {
int calculate(int a, int b);
}
Calculator add = (a, b) -> a + b;
Calculator subtract = (a, b) -> a - b;
Calculator multiply = (a, b) -> a * b;
int calcB = 0;
System.out.println(" 5 + " + calcB + " = " + add.calculate(5, calcB));
System.out.println(" 5 - " + calcB + " = " + subtract.calculate(5, calcB));
System.out.println(" 5 * " + calcB + " = " + multiply.calculate(5, calcB));
System.out.println("\nBlock body:");
Calculator divide = (a, b) -> {
if (b == 0) {
System.out.println(" Error: Division by zero");
return 0;
}
return a / b;
};
System.out.println(" 10 / " + calcB + " = " + divide.calculate(10, calcB));
System.out.println("\nExplicit types:");
Calculator power = (int base, int exp) -> {
int result = 1;
for (int i = 0; i < exp; i++) {
result *= base;
}
return result;
};
System.out.println(" 2^3 = " + power.calculate(2, 3));
System.out.println(" 5^2 = " + power.calculate(5, 2));
System.out.println("\nComparator:");
List<String> names = new ArrayList<>(Arrays.asList("Charlie", "Alice", "Bob"));
System.out.println(" Before: " + names);
names.sort((a, b) -> a.compareTo(b));
System.out.println(" Sorted: " + names);
names.sort((a, b) -> b.compareTo(a));
System.out.println(" Reverse: " + names);
}
}
import java.util.*;
public class Basic {
public static void main(String[] args) {
System.out.println("No parameters:\n");
Runnable task = () -> System.out.println(" Hello from lambda!");
task.run();
Runnable oldWay = new Runnable() {
@Override
public void run() {
System.out.println(" Hello from anonymous class");
}
};
oldWay.run();
System.out.println("\nSingle parameter:");
interface Printer {
void print(String message);
}
Printer p1 = message -> System.out.println(" " + message);
p1.print("No parentheses");
Printer p2 = (message) -> System.out.println(" " + message);
p2.print("With parentheses");
System.out.println("\nMultiple parameters:");
interface Calculator {
int calculate(int a, int b);
}
Calculator add = (a, b) -> a + b;
Calculator subtract = (a, b) -> a - b;
Calculator multiply = (a, b) -> a * b;
int calcB = 4;
System.out.println(" 5 + " + calcB + " = " + add.calculate(5, calcB));
System.out.println(" 5 - " + calcB + " = " + subtract.calculate(5, calcB));
System.out.println(" 5 * " + calcB + " = " + multiply.calculate(5, calcB));
System.out.println("\nBlock body:");
Calculator divide = (a, b) -> {
if (b == 0) {
System.out.println(" Error: Division by zero");
return 0;
}
return a / b;
};
System.out.println(" 10 / " + calcB + " = " + divide.calculate(10, calcB));
System.out.println("\nExplicit types:");
Calculator power = (int base, int exp) -> {
int result = 1;
for (int i = 0; i < exp; i++) {
result *= base;
}
return result;
};
System.out.println(" 2^3 = " + power.calculate(2, 3));
System.out.println(" 5^2 = " + power.calculate(5, 2));
System.out.println("\nComparator:");
List<String> names = new ArrayList<>(Arrays.asList("Charlie", "Alice", "Bob"));
System.out.println(" Before: " + names);
names.sort((a, b) -> a.compareTo(b));
System.out.println(" Sorted: " + names);
names.sort((a, b) -> b.compareTo(a));
System.out.println(" Reverse: " + names);
}
}
task ← ⟨Basic lambda A⟩, oldWay ← ⟨Basic$1 B⟩
3public class Basic {4 public static void main(String[] args) {5 System.out.println("No parameters:\n");6 7 Runnable task→ ⟨Basic lambda A⟩ = () -> System.out.println(" Hello from lambda!");8 task.run();9 10 Runnable oldWay→ ⟨Basic$1 B⟩ = new Runnable() {11 @Override12 public void run() {13 System.out.println(" Hello from anonymous class");14 }15 };16 oldWay.run();outputNo parameters:@Override public void run()
10Runnable oldWay = new Runnable() {11 @Override12 public void run() {13 System.out.println(" Hello from anonymous class");14 }output Hello from anonymous classp1 ← ⟨Basic lambda C⟩, p2 ← ⟨Basic lambda D⟩, add ← ⟨Basic lambda E⟩
15};16oldWay.run();171819System.out.println("\nSingle parameter:");2021interface Printer {22 void print(String message);23}2425Printer p1→ ⟨Basic lambda C⟩ = message -> System.out.println(" " + message);26p1.print("No parentheses");2728Printer p2→ ⟨Basic lambda D⟩ = (message) -> System.out.println(" " + message);29p2.print("With parentheses");3031System.out.println("\nMultiple parameters:");3233interface Calculator {34 int calculate(int a, int b);35}3637Calculator add→ ⟨Basic lambda E⟩ = (a, b) -> a + b;38Calculator subtract→ ⟨Basic lambda F⟩ = (a, b) -> a - b;39Calculator multiply→ ⟨Basic lambda G⟩ = (a, b) -> a * b;4041int calcB→ 3 = 3; //@calcB=3, 0, 442System.out.println(" 5 + " + calcB3 + " = " + add.calculate(5, calcB));43System.out.println(" 5 - " + calcB3 + " = " + subtract.calculate(5, calcB));44System.out.println(" 5 * " + calcB3 + " = " + multiply.calculate(5, calcB));4546System.out.println("\nBlock body:");4748Calculator divide→ ⟨Basic lambda H⟩ = (a, b) -> {49 if (b == 0) {50 System.out.println(" Error: Division by zero");51 return 0;52 }53 return a / b;54};5556System.out.println(" 10 / " + calcB3 + " = " + divide.calculate(10, calcB));output Single parameter: Multiple parameters: 5 + 3 = 8 5 - 3 = 2 5 * 3 = 15 Block body:power ← ⟨Basic lambda I⟩
56System.out.println(" 10 / " + calcB3 + " = " + divide.calculate(10, calcB));5758System.out.println("\nExplicit types:");5960Calculator power→ ⟨Basic lambda I⟩ = (int base, int exp) -> {61 int result = 1;62 for (int i = 0; i < exp; i++) {63 result *= base;64 }65 return result;66};6768System.out.println(" 2^3 = " + power.calculate(2, 3));69System.out.println(" 5^2 = " + power.calculate(5, 2));output 10 / 3 = 3 Explicit types:return result;
64 }65 return result;66};System.out.println(" 2^3 = " + power.calculate(2, 3));
68System.out.println(" 2^3 = " + power.calculate(2, 3));69System.out.println(" 5^2 = " + power.calculate(5, 2));output 2^3 = 8return result;
64 }65 return result;66};names ← [Charlie, Alice, Bob]
68 System.out.println(" 2^3 = " + power.calculate(2, 3));69 System.out.println(" 5^2 = " + power.calculate(5, 2));70 71 System.out.println("\nComparator:");72 73 List<String> names→ [Charlie, Alice, Bob] = new ArrayList<>(Arrays.asList("Charlie", "Alice", "Bob"));74 System.out.println(" Before: " + names[Charlie, Alice, Bob]);75 76 names.sort((a, b) -> a.compareTo(b));77 System.out.println(" Sorted: " + names[Alice, Bob, Charlie]);78 79 names.sort((a, b) -> b.compareTo(a));80 System.out.println(" Reverse: " + names[Charlie, Bob, Alice]);81}output 5^2 = 25 Comparator: Before: [Charlie, Alice, Bob] Sorted: [Alice, Bob, Charlie] Reverse: [Charlie, Bob, Alice]
task ← ⟨Basic lambda A⟩, oldWay ← ⟨Basic$1 B⟩
3public class Basic {4 public static void main(String[] args) {5 System.out.println("No parameters:\n");6 7 Runnable task→ ⟨Basic lambda A⟩ = () -> System.out.println(" Hello from lambda!");8 task.run();9 10 Runnable oldWay→ ⟨Basic$1 B⟩ = new Runnable() {11 @Override12 public void run() {13 System.out.println(" Hello from anonymous class");14 }15 };16 oldWay.run();outputNo parameters:@Override public void run()
10Runnable oldWay = new Runnable() {11 @Override12 public void run() {13 System.out.println(" Hello from anonymous class");14 }output Hello from anonymous classp1 ← ⟨Basic lambda C⟩, p2 ← ⟨Basic lambda D⟩, add ← ⟨Basic lambda E⟩
15};16oldWay.run();171819System.out.println("\nSingle parameter:");2021interface Printer {22 void print(String message);23}2425Printer p1→ ⟨Basic lambda C⟩ = message -> System.out.println(" " + message);26p1.print("No parentheses");2728Printer p2→ ⟨Basic lambda D⟩ = (message) -> System.out.println(" " + message);29p2.print("With parentheses");3031System.out.println("\nMultiple parameters:");3233interface Calculator {34 int calculate(int a, int b);35}3637Calculator add→ ⟨Basic lambda E⟩ = (a, b) -> a + b;38Calculator subtract→ ⟨Basic lambda F⟩ = (a, b) -> a - b;39Calculator multiply→ ⟨Basic lambda G⟩ = (a, b) -> a * b;4041int calcB→ 0 = 0;42System.out.println(" 5 + " + calcB0 + " = " + add.calculate(5, calcB));43System.out.println(" 5 - " + calcB0 + " = " + subtract.calculate(5, calcB));44System.out.println(" 5 * " + calcB0 + " = " + multiply.calculate(5, calcB));4546System.out.println("\nBlock body:");4748Calculator divide→ ⟨Basic lambda H⟩ = (a, b) -> {49 if (b == 0) {50 System.out.println(" Error: Division by zero");51 return 0;52 }53 return a / b;54};5556System.out.println(" 10 / " + calcB0 + " = " + divide.calculate(10, calcB));output Single parameter: Multiple parameters: 5 + 0 = 5 5 - 0 = 5 5 * 0 = 0 Block body:if (b == 0)
48Calculator divide = (a, b) -> {49 if (b == 0) {50 System.out.println(" Error: Division by zero");51 return 0;52 }output Error: Division by zeropower ← ⟨Basic lambda I⟩
56System.out.println(" 10 / " + calcB0 + " = " + divide.calculate(10, calcB));5758System.out.println("\nExplicit types:");5960Calculator power→ ⟨Basic lambda I⟩ = (int base, int exp) -> {61 int result = 1;62 for (int i = 0; i < exp; i++) {63 result *= base;64 }65 return result;66};6768System.out.println(" 2^3 = " + power.calculate(2, 3));69System.out.println(" 5^2 = " + power.calculate(5, 2));output 10 / 0 = 0 Explicit types:return result;
64 }65 return result;66};System.out.println(" 2^3 = " + power.calculate(2, 3));
68System.out.println(" 2^3 = " + power.calculate(2, 3));69System.out.println(" 5^2 = " + power.calculate(5, 2));output 2^3 = 8return result;
64 }65 return result;66};names ← [Charlie, Alice, Bob]
68 System.out.println(" 2^3 = " + power.calculate(2, 3));69 System.out.println(" 5^2 = " + power.calculate(5, 2));70 71 System.out.println("\nComparator:");72 73 List<String> names→ [Charlie, Alice, Bob] = new ArrayList<>(Arrays.asList("Charlie", "Alice", "Bob"));74 System.out.println(" Before: " + names[Charlie, Alice, Bob]);75 76 names.sort((a, b) -> a.compareTo(b));77 System.out.println(" Sorted: " + names[Alice, Bob, Charlie]);78 79 names.sort((a, b) -> b.compareTo(a));80 System.out.println(" Reverse: " + names[Charlie, Bob, Alice]);81}output 5^2 = 25 Comparator: Before: [Charlie, Alice, Bob] Sorted: [Alice, Bob, Charlie] Reverse: [Charlie, Bob, Alice]
task ← ⟨Basic lambda A⟩, oldWay ← ⟨Basic$1 B⟩
3public class Basic {4 public static void main(String[] args) {5 System.out.println("No parameters:\n");6 7 Runnable task→ ⟨Basic lambda A⟩ = () -> System.out.println(" Hello from lambda!");8 task.run();9 10 Runnable oldWay→ ⟨Basic$1 B⟩ = new Runnable() {11 @Override12 public void run() {13 System.out.println(" Hello from anonymous class");14 }15 };16 oldWay.run();outputNo parameters:@Override public void run()
10Runnable oldWay = new Runnable() {11 @Override12 public void run() {13 System.out.println(" Hello from anonymous class");14 }output Hello from anonymous classp1 ← ⟨Basic lambda C⟩, p2 ← ⟨Basic lambda D⟩, add ← ⟨Basic lambda E⟩
15};16oldWay.run();171819System.out.println("\nSingle parameter:");2021interface Printer {22 void print(String message);23}2425Printer p1→ ⟨Basic lambda C⟩ = message -> System.out.println(" " + message);26p1.print("No parentheses");2728Printer p2→ ⟨Basic lambda D⟩ = (message) -> System.out.println(" " + message);29p2.print("With parentheses");3031System.out.println("\nMultiple parameters:");3233interface Calculator {34 int calculate(int a, int b);35}3637Calculator add→ ⟨Basic lambda E⟩ = (a, b) -> a + b;38Calculator subtract→ ⟨Basic lambda F⟩ = (a, b) -> a - b;39Calculator multiply→ ⟨Basic lambda G⟩ = (a, b) -> a * b;4041int calcB→ 4 = 4;42System.out.println(" 5 + " + calcB4 + " = " + add.calculate(5, calcB));43System.out.println(" 5 - " + calcB4 + " = " + subtract.calculate(5, calcB));44System.out.println(" 5 * " + calcB4 + " = " + multiply.calculate(5, calcB));4546System.out.println("\nBlock body:");4748Calculator divide→ ⟨Basic lambda H⟩ = (a, b) -> {49 if (b == 0) {50 System.out.println(" Error: Division by zero");51 return 0;52 }53 return a / b;54};5556System.out.println(" 10 / " + calcB4 + " = " + divide.calculate(10, calcB));output Single parameter: Multiple parameters: 5 + 4 = 9 5 - 4 = 1 5 * 4 = 20 Block body:power ← ⟨Basic lambda I⟩
56System.out.println(" 10 / " + calcB4 + " = " + divide.calculate(10, calcB));5758System.out.println("\nExplicit types:");5960Calculator power→ ⟨Basic lambda I⟩ = (int base, int exp) -> {61 int result = 1;62 for (int i = 0; i < exp; i++) {63 result *= base;64 }65 return result;66};6768System.out.println(" 2^3 = " + power.calculate(2, 3));69System.out.println(" 5^2 = " + power.calculate(5, 2));output 10 / 4 = 2 Explicit types:return result;
64 }65 return result;66};System.out.println(" 2^3 = " + power.calculate(2, 3));
68System.out.println(" 2^3 = " + power.calculate(2, 3));69System.out.println(" 5^2 = " + power.calculate(5, 2));output 2^3 = 8return result;
64 }65 return result;66};names ← [Charlie, Alice, Bob]
68 System.out.println(" 2^3 = " + power.calculate(2, 3));69 System.out.println(" 5^2 = " + power.calculate(5, 2));70 71 System.out.println("\nComparator:");72 73 List<String> names→ [Charlie, Alice, Bob] = new ArrayList<>(Arrays.asList("Charlie", "Alice", "Bob"));74 System.out.println(" Before: " + names[Charlie, Alice, Bob]);75 76 names.sort((a, b) -> a.compareTo(b));77 System.out.println(" Sorted: " + names[Alice, Bob, Charlie]);78 79 names.sort((a, b) -> b.compareTo(a));80 System.out.println(" Reverse: " + names[Charlie, Bob, Alice]);81}output 5^2 = 25 Comparator: Before: [Charlie, Alice, Bob] Sorted: [Alice, Bob, Charlie] Reverse: [Charlie, Bob, Alice]
(params) -> expression - concise syntax for single-method interfaces.
lambda
Anonymous function: `(x, y) -> x + y`. Implements functional interface.
Lambda parameters
Different ways to specify parameters.
Parameters.java
Replay: real traced execution (multi-file project)
import java.util.*;
import java.util.function.*;
public class Parameters {
public static void main(String[] args) {
System.out.println("Single parameter:\n");
UnaryOperator<Integer> square = x -> x * x;
UnaryOperator<Integer> doubler = x -> x * 2;
UnaryOperator<String> upper = s -> s.toUpperCase();
System.out.println(" square(5) = " + square.apply(5));
System.out.println(" doubler(7) = " + doubler.apply(7));
System.out.println(" upper('hello') = " + upper.apply("hello"));
System.out.println("\nTwo parameters:");
BinaryOperator<Integer> max = (a, b) -> a > b ? a : b;
BinaryOperator<Integer> min = (a, b) -> a < b ? a : b;
BinaryOperator<String> concat = (s1, s2) -> s1 + s2;
System.out.println(" max(10, 20) = " + max.apply(10, 20));
System.out.println(" min(10, 20) = " + min.apply(10, 20));
System.out.println(" concat('Hello', ' World') = " + concat.apply("Hello", " World"));
System.out.println("\nDifferent input/output types:");
BiFunction<String, Integer, String> repeat = (str, n) -> {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < n; i++) {
sb.append(str);
}
return sb.toString();
};
BiFunction<Integer, Integer, Double> divide = (a, b) -> (double) a / b;
int repeatCount = 3;
System.out.println(" repeat('ab', " + repeatCount + ") = " +
repeat.apply("ab", repeatCount));
System.out.println(" divide(10, 4) = " + divide.apply(10, 4));
System.out.println("\nBlock with parameters:");
BiFunction<Integer, Integer, String> compare = (a, b) -> {
if (a > b) {
return a + " is greater";
} else if (a < b) {
return b + " is greater";
} else {
return "Equal";
}
};
System.out.println(" compare(10, 5): " + compare.apply(10, 5));
System.out.println(" compare(3, 8): " + compare.apply(3, 8));
System.out.println(" compare(7, 7): " + compare.apply(7, 7));
System.out.println("\nList operations:");
List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
System.out.print(" Numbers: ");
numbers.forEach(n -> System.out.print(n + " "));
System.out.println();
numbers.removeIf(n -> n % 2 == 0);
System.out.println(" After removing evens: " + numbers);
System.out.println("\nCustom interface:");
interface Validator {
boolean validate(String input);
}
Validator notEmpty = s -> s != null && !s.isEmpty();
Validator isEmail = s -> s.contains("@");
Validator minLength = s -> s.length() >= 5;
String test1 = "user@example.com";
String test2 = "ab";
System.out.println(" '" + test1 + "' not empty: " + notEmpty.validate(test1));
System.out.println(" '" + test1 + "' is email: " + isEmail.validate(test1));
System.out.println(" '" + test2 + "' min length: " + minLength.validate(test2));
}
}
import java.util.*;
import java.util.function.*;
public class Parameters {
public static void main(String[] args) {
System.out.println("Single parameter:\n");
UnaryOperator<Integer> square = x -> x * x;
UnaryOperator<Integer> doubler = x -> x * 2;
UnaryOperator<String> upper = s -> s.toUpperCase();
System.out.println(" square(5) = " + square.apply(5));
System.out.println(" doubler(7) = " + doubler.apply(7));
System.out.println(" upper('hello') = " + upper.apply("hello"));
System.out.println("\nTwo parameters:");
BinaryOperator<Integer> max = (a, b) -> a > b ? a : b;
BinaryOperator<Integer> min = (a, b) -> a < b ? a : b;
BinaryOperator<String> concat = (s1, s2) -> s1 + s2;
System.out.println(" max(10, 20) = " + max.apply(10, 20));
System.out.println(" min(10, 20) = " + min.apply(10, 20));
System.out.println(" concat('Hello', ' World') = " + concat.apply("Hello", " World"));
System.out.println("\nDifferent input/output types:");
BiFunction<String, Integer, String> repeat = (str, n) -> {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < n; i++) {
sb.append(str);
}
return sb.toString();
};
BiFunction<Integer, Integer, Double> divide = (a, b) -> (double) a / b;
int repeatCount = 1;
System.out.println(" repeat('ab', " + repeatCount + ") = " +
repeat.apply("ab", repeatCount));
System.out.println(" divide(10, 4) = " + divide.apply(10, 4));
System.out.println("\nBlock with parameters:");
BiFunction<Integer, Integer, String> compare = (a, b) -> {
if (a > b) {
return a + " is greater";
} else if (a < b) {
return b + " is greater";
} else {
return "Equal";
}
};
System.out.println(" compare(10, 5): " + compare.apply(10, 5));
System.out.println(" compare(3, 8): " + compare.apply(3, 8));
System.out.println(" compare(7, 7): " + compare.apply(7, 7));
System.out.println("\nList operations:");
List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
System.out.print(" Numbers: ");
numbers.forEach(n -> System.out.print(n + " "));
System.out.println();
numbers.removeIf(n -> n % 2 == 0);
System.out.println(" After removing evens: " + numbers);
System.out.println("\nCustom interface:");
interface Validator {
boolean validate(String input);
}
Validator notEmpty = s -> s != null && !s.isEmpty();
Validator isEmail = s -> s.contains("@");
Validator minLength = s -> s.length() >= 5;
String test1 = "user@example.com";
String test2 = "ab";
System.out.println(" '" + test1 + "' not empty: " + notEmpty.validate(test1));
System.out.println(" '" + test1 + "' is email: " + isEmail.validate(test1));
System.out.println(" '" + test2 + "' min length: " + minLength.validate(test2));
}
}
import java.util.*;
import java.util.function.*;
public class Parameters {
public static void main(String[] args) {
System.out.println("Single parameter:\n");
UnaryOperator<Integer> square = x -> x * x;
UnaryOperator<Integer> doubler = x -> x * 2;
UnaryOperator<String> upper = s -> s.toUpperCase();
System.out.println(" square(5) = " + square.apply(5));
System.out.println(" doubler(7) = " + doubler.apply(7));
System.out.println(" upper('hello') = " + upper.apply("hello"));
System.out.println("\nTwo parameters:");
BinaryOperator<Integer> max = (a, b) -> a > b ? a : b;
BinaryOperator<Integer> min = (a, b) -> a < b ? a : b;
BinaryOperator<String> concat = (s1, s2) -> s1 + s2;
System.out.println(" max(10, 20) = " + max.apply(10, 20));
System.out.println(" min(10, 20) = " + min.apply(10, 20));
System.out.println(" concat('Hello', ' World') = " + concat.apply("Hello", " World"));
System.out.println("\nDifferent input/output types:");
BiFunction<String, Integer, String> repeat = (str, n) -> {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < n; i++) {
sb.append(str);
}
return sb.toString();
};
BiFunction<Integer, Integer, Double> divide = (a, b) -> (double) a / b;
int repeatCount = 5;
System.out.println(" repeat('ab', " + repeatCount + ") = " +
repeat.apply("ab", repeatCount));
System.out.println(" divide(10, 4) = " + divide.apply(10, 4));
System.out.println("\nBlock with parameters:");
BiFunction<Integer, Integer, String> compare = (a, b) -> {
if (a > b) {
return a + " is greater";
} else if (a < b) {
return b + " is greater";
} else {
return "Equal";
}
};
System.out.println(" compare(10, 5): " + compare.apply(10, 5));
System.out.println(" compare(3, 8): " + compare.apply(3, 8));
System.out.println(" compare(7, 7): " + compare.apply(7, 7));
System.out.println("\nList operations:");
List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
System.out.print(" Numbers: ");
numbers.forEach(n -> System.out.print(n + " "));
System.out.println();
numbers.removeIf(n -> n % 2 == 0);
System.out.println(" After removing evens: " + numbers);
System.out.println("\nCustom interface:");
interface Validator {
boolean validate(String input);
}
Validator notEmpty = s -> s != null && !s.isEmpty();
Validator isEmail = s -> s.contains("@");
Validator minLength = s -> s.length() >= 5;
String test1 = "user@example.com";
String test2 = "ab";
System.out.println(" '" + test1 + "' not empty: " + notEmpty.validate(test1));
System.out.println(" '" + test1 + "' is email: " + isEmail.validate(test1));
System.out.println(" '" + test2 + "' min length: " + minLength.validate(test2));
}
}
square ← ⟨Parameters lambda A⟩, doubler ← ⟨Parameters lambda B⟩
4public class Parameters {5 public static void main(String[] args) {6 System.out.println("Single parameter:\n");7 8 UnaryOperator<Integer> square→ ⟨Parameters lambda A⟩ = x -> x * x;9 UnaryOperator<Integer> doubler→ ⟨Parameters lambda B⟩ = x -> x * 2;10 UnaryOperator<String> upper→ ⟨Parameters lambda C⟩ = s -> s.toUpperCase();11 12 System.out.println(" square(5) = " + square.apply(5));13 System.out.println(" doubler(7) = " + doubler.apply(7));14 System.out.println(" upper('hello') = " + upper.apply("hello"));15 16 17 System.out.println("\nTwo parameters:");18 19 BinaryOperator<Integer> max→ ⟨Parameters lambda D⟩ = (a, b) -> a > b ? a : b;20 BinaryOperator<Integer> min→ ⟨Parameters lambda E⟩ = (a, b) -> a < b ? a : b;21 BinaryOperator<String> concat→ ⟨Parameters lambda F⟩ = (s1, s2) -> s1 + s2;22 23 System.out.println(" max(10, 20) = " + max.apply(10, 20));24 System.out.println(" min(10, 20) = " + min.apply(10, 20));25 System.out.println(" concat('Hello', ' World') = " + concat.apply("Hello", " World"));26 27 System.out.println("\nDifferent input/output types:");28 29 BiFunction<String, Integer, String> repeat→ ⟨Parameters lambda G⟩ = (str, n) -> {30 StringBuilder sb = new StringBuilder();31 for (int i = 0; i < n; i++) {32 sb.append(str);33 }34 return sb.toString();35 };36 37 BiFunction<Integer, Integer, Double> divide→ ⟨Parameters lambda H⟩ = (a, b) -> (double) a / b;38 39 int repeatCount→ 3 = 3; //@repeatCount=3, 1, 540 System.out.println(" repeat('ab', " + repeatCount3 + ") = " +41 repeat.apply("ab", repeatCount3));42 System.out.println(" divide(10, 4) = " + divide.apply(10, 4));outputSingle parameter: square(5) = 25 doubler(7) = 14 upper('hello') = HELLO Two parameters: max(10, 20) = 20 min(10, 20) = 10 concat('Hello', ' World') = Hello World Different input/output types:return sb.toString();
33 }34 return sb.toString();35};compare ← ⟨Parameters lambda I⟩
39int repeatCount = 3; //@repeatCount=3, 1, 540System.out.println(" repeat('ab', " + repeatCount3 + ") = " +41 repeat.apply("ab", repeatCount3));42System.out.println(" divide(10, 4) = " + divide.apply(10, 4));4344System.out.println("\nBlock with parameters:");4546BiFunction<Integer, Integer, String> compare→ ⟨Parameters lambda I⟩ = (a, b) -> {47 if (a > b) {48 return a + " is greater";49 } else if (a < b) {50 return b + " is greater";51 } else {52 return "Equal";53 }54};5556System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));output repeat('ab', 3) = ababab divide(10, 4) = 2.5 Block with parameters:System.out.println(" compare(10, 5): " + compare.apply(10, 5));
56System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));58System.out.println(" compare(7, 7): " + compare.apply(7, 7));output compare(10, 5): 10 is greaterSystem.out.println(" compare(3, 8): " + compare.apply(3, 8));
56System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));58System.out.println(" compare(7, 7): " + compare.apply(7, 7));output compare(3, 8): 8 is greaternumbers ← [1, 2, 3, 4, 5], notEmpty ← ⟨Parameters lambda J⟩, isEmail ← ⟨Parameters lambda K⟩
57 System.out.println(" compare(3, 8): " + compare.apply(3, 8));58 System.out.println(" compare(7, 7): " + compare.apply(7, 7));59 60 System.out.println("\nList operations:");61 62 List<Integer> numbers→ [1, 2, 3, 4, 5] = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));63 64 System.out.print(" Numbers: ");65 numbers.forEach(n -> System.out.print(n + " "));66 System.out.println();67 68 numbers.removeIf(n -> n % 2 == 0);69 System.out.println(" After removing evens: " + numbers[1, 3, 5]);70 71 System.out.println("\nCustom interface:");72 73 interface Validator {74 boolean validate(String input);75 }76 77 Validator notEmpty→ ⟨Parameters lambda J⟩ = s -> s != null && !s.isEmpty();78 Validator isEmail→ ⟨Parameters lambda K⟩ = s -> s.contains("@");79 Validator minLength→ ⟨Parameters lambda L⟩ = s -> s.length() >= 5;80 81 String test1→ user@example.com = "user@example.com";82 String test2→ ab = "ab";83 84 System.out.println(" '" + test1user@example.com + "' not empty: " + notEmpty.validate(test1));85 System.out.println(" '" + test1user@example.com + "' is email: " + isEmail.validate(test1));86 System.out.println(" '" + test2ab + "' min length: " + minLength.validate(test2));87}output compare(7, 7): Equal List operations: Numbers: After removing evens: [1, 3, 5] Custom interface: 'user@example.com' not empty: true 'user@example.com' is email: true 'ab' min length: false
square ← ⟨Parameters lambda A⟩, doubler ← ⟨Parameters lambda B⟩
4public class Parameters {5 public static void main(String[] args) {6 System.out.println("Single parameter:\n");7 8 UnaryOperator<Integer> square→ ⟨Parameters lambda A⟩ = x -> x * x;9 UnaryOperator<Integer> doubler→ ⟨Parameters lambda B⟩ = x -> x * 2;10 UnaryOperator<String> upper→ ⟨Parameters lambda C⟩ = s -> s.toUpperCase();11 12 System.out.println(" square(5) = " + square.apply(5));13 System.out.println(" doubler(7) = " + doubler.apply(7));14 System.out.println(" upper('hello') = " + upper.apply("hello"));15 16 17 System.out.println("\nTwo parameters:");18 19 BinaryOperator<Integer> max→ ⟨Parameters lambda D⟩ = (a, b) -> a > b ? a : b;20 BinaryOperator<Integer> min→ ⟨Parameters lambda E⟩ = (a, b) -> a < b ? a : b;21 BinaryOperator<String> concat→ ⟨Parameters lambda F⟩ = (s1, s2) -> s1 + s2;22 23 System.out.println(" max(10, 20) = " + max.apply(10, 20));24 System.out.println(" min(10, 20) = " + min.apply(10, 20));25 System.out.println(" concat('Hello', ' World') = " + concat.apply("Hello", " World"));26 27 System.out.println("\nDifferent input/output types:");28 29 BiFunction<String, Integer, String> repeat→ ⟨Parameters lambda G⟩ = (str, n) -> {30 StringBuilder sb = new StringBuilder();31 for (int i = 0; i < n; i++) {32 sb.append(str);33 }34 return sb.toString();35 };36 37 BiFunction<Integer, Integer, Double> divide→ ⟨Parameters lambda H⟩ = (a, b) -> (double) a / b;38 39 int repeatCount→ 1 = 1;40 System.out.println(" repeat('ab', " + repeatCount1 + ") = " +41 repeat.apply("ab", repeatCount1));42 System.out.println(" divide(10, 4) = " + divide.apply(10, 4));outputSingle parameter: square(5) = 25 doubler(7) = 14 upper('hello') = HELLO Two parameters: max(10, 20) = 20 min(10, 20) = 10 concat('Hello', ' World') = Hello World Different input/output types:return sb.toString();
33 }34 return sb.toString();35};compare ← ⟨Parameters lambda I⟩
39int repeatCount = 1;40System.out.println(" repeat('ab', " + repeatCount1 + ") = " +41 repeat.apply("ab", repeatCount1));42System.out.println(" divide(10, 4) = " + divide.apply(10, 4));4344System.out.println("\nBlock with parameters:");4546BiFunction<Integer, Integer, String> compare→ ⟨Parameters lambda I⟩ = (a, b) -> {47 if (a > b) {48 return a + " is greater";49 } else if (a < b) {50 return b + " is greater";51 } else {52 return "Equal";53 }54};5556System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));output repeat('ab', 1) = ab divide(10, 4) = 2.5 Block with parameters:System.out.println(" compare(10, 5): " + compare.apply(10, 5));
56System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));58System.out.println(" compare(7, 7): " + compare.apply(7, 7));output compare(10, 5): 10 is greaterSystem.out.println(" compare(3, 8): " + compare.apply(3, 8));
56System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));58System.out.println(" compare(7, 7): " + compare.apply(7, 7));output compare(3, 8): 8 is greaternumbers ← [1, 2, 3, 4, 5], notEmpty ← ⟨Parameters lambda J⟩, isEmail ← ⟨Parameters lambda K⟩
57 System.out.println(" compare(3, 8): " + compare.apply(3, 8));58 System.out.println(" compare(7, 7): " + compare.apply(7, 7));59 60 System.out.println("\nList operations:");61 62 List<Integer> numbers→ [1, 2, 3, 4, 5] = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));63 64 System.out.print(" Numbers: ");65 numbers.forEach(n -> System.out.print(n + " "));66 System.out.println();67 68 numbers.removeIf(n -> n % 2 == 0);69 System.out.println(" After removing evens: " + numbers[1, 3, 5]);70 71 System.out.println("\nCustom interface:");72 73 interface Validator {74 boolean validate(String input);75 }76 77 Validator notEmpty→ ⟨Parameters lambda J⟩ = s -> s != null && !s.isEmpty();78 Validator isEmail→ ⟨Parameters lambda K⟩ = s -> s.contains("@");79 Validator minLength→ ⟨Parameters lambda L⟩ = s -> s.length() >= 5;80 81 String test1→ user@example.com = "user@example.com";82 String test2→ ab = "ab";83 84 System.out.println(" '" + test1user@example.com + "' not empty: " + notEmpty.validate(test1));85 System.out.println(" '" + test1user@example.com + "' is email: " + isEmail.validate(test1));86 System.out.println(" '" + test2ab + "' min length: " + minLength.validate(test2));87}output compare(7, 7): Equal List operations: Numbers: After removing evens: [1, 3, 5] Custom interface: 'user@example.com' not empty: true 'user@example.com' is email: true 'ab' min length: false
square ← ⟨Parameters lambda A⟩, doubler ← ⟨Parameters lambda B⟩
4public class Parameters {5 public static void main(String[] args) {6 System.out.println("Single parameter:\n");7 8 UnaryOperator<Integer> square→ ⟨Parameters lambda A⟩ = x -> x * x;9 UnaryOperator<Integer> doubler→ ⟨Parameters lambda B⟩ = x -> x * 2;10 UnaryOperator<String> upper→ ⟨Parameters lambda C⟩ = s -> s.toUpperCase();11 12 System.out.println(" square(5) = " + square.apply(5));13 System.out.println(" doubler(7) = " + doubler.apply(7));14 System.out.println(" upper('hello') = " + upper.apply("hello"));15 16 17 System.out.println("\nTwo parameters:");18 19 BinaryOperator<Integer> max→ ⟨Parameters lambda D⟩ = (a, b) -> a > b ? a : b;20 BinaryOperator<Integer> min→ ⟨Parameters lambda E⟩ = (a, b) -> a < b ? a : b;21 BinaryOperator<String> concat→ ⟨Parameters lambda F⟩ = (s1, s2) -> s1 + s2;22 23 System.out.println(" max(10, 20) = " + max.apply(10, 20));24 System.out.println(" min(10, 20) = " + min.apply(10, 20));25 System.out.println(" concat('Hello', ' World') = " + concat.apply("Hello", " World"));26 27 System.out.println("\nDifferent input/output types:");28 29 BiFunction<String, Integer, String> repeat→ ⟨Parameters lambda G⟩ = (str, n) -> {30 StringBuilder sb = new StringBuilder();31 for (int i = 0; i < n; i++) {32 sb.append(str);33 }34 return sb.toString();35 };36 37 BiFunction<Integer, Integer, Double> divide→ ⟨Parameters lambda H⟩ = (a, b) -> (double) a / b;38 39 int repeatCount→ 5 = 5;40 System.out.println(" repeat('ab', " + repeatCount5 + ") = " +41 repeat.apply("ab", repeatCount5));42 System.out.println(" divide(10, 4) = " + divide.apply(10, 4));outputSingle parameter: square(5) = 25 doubler(7) = 14 upper('hello') = HELLO Two parameters: max(10, 20) = 20 min(10, 20) = 10 concat('Hello', ' World') = Hello World Different input/output types:return sb.toString();
33 }34 return sb.toString();35};compare ← ⟨Parameters lambda I⟩
39int repeatCount = 5;40System.out.println(" repeat('ab', " + repeatCount5 + ") = " +41 repeat.apply("ab", repeatCount5));42System.out.println(" divide(10, 4) = " + divide.apply(10, 4));4344System.out.println("\nBlock with parameters:");4546BiFunction<Integer, Integer, String> compare→ ⟨Parameters lambda I⟩ = (a, b) -> {47 if (a > b) {48 return a + " is greater";49 } else if (a < b) {50 return b + " is greater";51 } else {52 return "Equal";53 }54};5556System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));output repeat('ab', 5) = ababababab divide(10, 4) = 2.5 Block with parameters:System.out.println(" compare(10, 5): " + compare.apply(10, 5));
56System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));58System.out.println(" compare(7, 7): " + compare.apply(7, 7));output compare(10, 5): 10 is greaterSystem.out.println(" compare(3, 8): " + compare.apply(3, 8));
56System.out.println(" compare(10, 5): " + compare.apply(10, 5));57System.out.println(" compare(3, 8): " + compare.apply(3, 8));58System.out.println(" compare(7, 7): " + compare.apply(7, 7));output compare(3, 8): 8 is greaternumbers ← [1, 2, 3, 4, 5], notEmpty ← ⟨Parameters lambda J⟩, isEmail ← ⟨Parameters lambda K⟩
57 System.out.println(" compare(3, 8): " + compare.apply(3, 8));58 System.out.println(" compare(7, 7): " + compare.apply(7, 7));59 60 System.out.println("\nList operations:");61 62 List<Integer> numbers→ [1, 2, 3, 4, 5] = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));63 64 System.out.print(" Numbers: ");65 numbers.forEach(n -> System.out.print(n + " "));66 System.out.println();67 68 numbers.removeIf(n -> n % 2 == 0);69 System.out.println(" After removing evens: " + numbers[1, 3, 5]);70 71 System.out.println("\nCustom interface:");72 73 interface Validator {74 boolean validate(String input);75 }76 77 Validator notEmpty→ ⟨Parameters lambda J⟩ = s -> s != null && !s.isEmpty();78 Validator isEmail→ ⟨Parameters lambda K⟩ = s -> s.contains("@");79 Validator minLength→ ⟨Parameters lambda L⟩ = s -> s.length() >= 5;80 81 String test1→ user@example.com = "user@example.com";82 String test2→ ab = "ab";83 84 System.out.println(" '" + test1user@example.com + "' not empty: " + notEmpty.validate(test1));85 System.out.println(" '" + test1user@example.com + "' is email: " + isEmail.validate(test1));86 System.out.println(" '" + test2ab + "' min length: " + minLength.validate(test2));87}output compare(7, 7): Equal List operations: Numbers: After removing evens: [1, 3, 5] Custom interface: 'user@example.com' not empty: true 'user@example.com' is email: true 'ab' min length: false
x -> x*2 (one param, no parens), (x, y) -> x+y (multiple), (int x) -> x*2 (typed).
Block lambda
Multiple statements in lambda body.
Block.java
Replay: real traced execution (multi-file project)
import java.util.*;
import java.util.function.*;
public class Block {
public static void main(String[] args) {
System.out.println("Single vs block:\n");
Function<Integer, Integer> single = x -> x * 2;
Function<Integer, Integer> block = x -> {
int result = x * 2;
return result;
};
System.out.println(" Single: " + single.apply(5));
System.out.println(" Block: " + block.apply(5));
System.out.println("\nComplex logic:");
Function<Integer, String> classify = n -> {
if (n < 0) {
return "negative";
} else if (n == 0) {
return "zero";
} else if (n % 2 == 0) {
return "positive even";
} else {
return "positive odd";
}
};
System.out.println(" classify(-5): " + classify.apply(-5));
System.out.println(" classify(0): " + classify.apply(0));
System.out.println(" classify(4): " + classify.apply(4));
System.out.println(" classify(7): " + classify.apply(7));
System.out.println("\nLocal variables:");
BiFunction<Integer, Integer, Integer> gcd = (a, b) -> {
int temp;
while (b != 0) {
temp = b;
b = a % b;
a = temp;
}
return a;
};
System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));
System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));
System.out.println("\nValidation:");
Function<String, Boolean> isValidPassword = password -> {
if (password == null || password.length() < 8) {
return false;
}
boolean hasDigit = false;
boolean hasLetter = false;
for (char c : password.toCharArray()) {
if (Character.isDigit(c)) hasDigit = true;
if (Character.isLetter(c)) hasLetter = true;
}
return hasDigit && hasLetter;
};
String passwordToCheck = "abc123def";
System.out.println(" '" + passwordToCheck + "' valid: " +
isValidPassword.apply(passwordToCheck));
System.out.println(" 'short' valid: " + isValidPassword.apply("short"));
System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));
System.out.println("\nMulti-step processing:");
Function<List<Integer>, Double> average = list -> {
if (list.isEmpty()) {
return 0.0;
}
int sum = 0;
for (int n : list) {
sum += n;
}
return (double) sum / list.size();
};
List<Integer> scores = Arrays.asList(85, 90, 78, 92, 88);
System.out.println(" Average score: " + average.apply(scores));
System.out.println("\nException handling:");
BiFunction<Integer, Integer, Integer> safeDivide = (a, b) -> {
try {
return a / b;
} catch (ArithmeticException e) {
System.out.println(" Error: " + e.getMessage());
return 0;
}
};
System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));
System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));
}
}
import java.util.*;
import java.util.function.*;
public class Block {
public static void main(String[] args) {
System.out.println("Single vs block:\n");
Function<Integer, Integer> single = x -> x * 2;
Function<Integer, Integer> block = x -> {
int result = x * 2;
return result;
};
System.out.println(" Single: " + single.apply(5));
System.out.println(" Block: " + block.apply(5));
System.out.println("\nComplex logic:");
Function<Integer, String> classify = n -> {
if (n < 0) {
return "negative";
} else if (n == 0) {
return "zero";
} else if (n % 2 == 0) {
return "positive even";
} else {
return "positive odd";
}
};
System.out.println(" classify(-5): " + classify.apply(-5));
System.out.println(" classify(0): " + classify.apply(0));
System.out.println(" classify(4): " + classify.apply(4));
System.out.println(" classify(7): " + classify.apply(7));
System.out.println("\nLocal variables:");
BiFunction<Integer, Integer, Integer> gcd = (a, b) -> {
int temp;
while (b != 0) {
temp = b;
b = a % b;
a = temp;
}
return a;
};
System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));
System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));
System.out.println("\nValidation:");
Function<String, Boolean> isValidPassword = password -> {
if (password == null || password.length() < 8) {
return false;
}
boolean hasDigit = false;
boolean hasLetter = false;
for (char c : password.toCharArray()) {
if (Character.isDigit(c)) hasDigit = true;
if (Character.isLetter(c)) hasLetter = true;
}
return hasDigit && hasLetter;
};
String passwordToCheck = "short";
System.out.println(" '" + passwordToCheck + "' valid: " +
isValidPassword.apply(passwordToCheck));
System.out.println(" 'short' valid: " + isValidPassword.apply("short"));
System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));
System.out.println("\nMulti-step processing:");
Function<List<Integer>, Double> average = list -> {
if (list.isEmpty()) {
return 0.0;
}
int sum = 0;
for (int n : list) {
sum += n;
}
return (double) sum / list.size();
};
List<Integer> scores = Arrays.asList(85, 90, 78, 92, 88);
System.out.println(" Average score: " + average.apply(scores));
System.out.println("\nException handling:");
BiFunction<Integer, Integer, Integer> safeDivide = (a, b) -> {
try {
return a / b;
} catch (ArithmeticException e) {
System.out.println(" Error: " + e.getMessage());
return 0;
}
};
System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));
System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));
}
}
import java.util.*;
import java.util.function.*;
public class Block {
public static void main(String[] args) {
System.out.println("Single vs block:\n");
Function<Integer, Integer> single = x -> x * 2;
Function<Integer, Integer> block = x -> {
int result = x * 2;
return result;
};
System.out.println(" Single: " + single.apply(5));
System.out.println(" Block: " + block.apply(5));
System.out.println("\nComplex logic:");
Function<Integer, String> classify = n -> {
if (n < 0) {
return "negative";
} else if (n == 0) {
return "zero";
} else if (n % 2 == 0) {
return "positive even";
} else {
return "positive odd";
}
};
System.out.println(" classify(-5): " + classify.apply(-5));
System.out.println(" classify(0): " + classify.apply(0));
System.out.println(" classify(4): " + classify.apply(4));
System.out.println(" classify(7): " + classify.apply(7));
System.out.println("\nLocal variables:");
BiFunction<Integer, Integer, Integer> gcd = (a, b) -> {
int temp;
while (b != 0) {
temp = b;
b = a % b;
a = temp;
}
return a;
};
System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));
System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));
System.out.println("\nValidation:");
Function<String, Boolean> isValidPassword = password -> {
if (password == null || password.length() < 8) {
return false;
}
boolean hasDigit = false;
boolean hasLetter = false;
for (char c : password.toCharArray()) {
if (Character.isDigit(c)) hasDigit = true;
if (Character.isLetter(c)) hasLetter = true;
}
return hasDigit && hasLetter;
};
String passwordToCheck = "onlyletters";
System.out.println(" '" + passwordToCheck + "' valid: " +
isValidPassword.apply(passwordToCheck));
System.out.println(" 'short' valid: " + isValidPassword.apply("short"));
System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));
System.out.println("\nMulti-step processing:");
Function<List<Integer>, Double> average = list -> {
if (list.isEmpty()) {
return 0.0;
}
int sum = 0;
for (int n : list) {
sum += n;
}
return (double) sum / list.size();
};
List<Integer> scores = Arrays.asList(85, 90, 78, 92, 88);
System.out.println(" Average score: " + average.apply(scores));
System.out.println("\nException handling:");
BiFunction<Integer, Integer, Integer> safeDivide = (a, b) -> {
try {
return a / b;
} catch (ArithmeticException e) {
System.out.println(" Error: " + e.getMessage());
return 0;
}
};
System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));
System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));
}
}
single ← ⟨Block lambda A⟩, block ← ⟨Block lambda B⟩
4public class Block {5 public static void main(String[] args) {6 System.out.println("Single vs block:\n");7 8 Function<Integer, Integer> single→ ⟨Block lambda A⟩ = x -> x * 2;9 10 Function<Integer, Integer> block→ ⟨Block lambda B⟩ = x -> {11 int result = x * 2;12 return result;13 };14 15 System.out.println(" Single: " + single.apply(5));16 System.out.println(" Block: " + block.apply(5));outputSingle vs block: Single: 10classify ← ⟨Block lambda C⟩
15System.out.println(" Single: " + single.apply(5));16System.out.println(" Block: " + block.apply(5));171819System.out.println("\nComplex logic:");2021Function<Integer, String> classify→ ⟨Block lambda C⟩ = n -> {22 if (n < 0) {23 return "negative";24 } else if (n == 0) {25 return "zero";26 } else if (n % 2 == 0) {27 return "positive even";28 } else {29 return "positive odd";30 }31};3233System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));output Block: 10 Complex logic:System.out.println(" classify(-5): " + classify.apply(-5));
33System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));output classify(-5): negativeSystem.out.println(" classify(0): " + classify.apply(0));
33System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));output classify(0): zeroSystem.out.println(" classify(4): " + classify.apply(4));
34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));output classify(4): positive evengcd ← ⟨Block lambda D⟩
35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));3738System.out.println("\nLocal variables:");3940BiFunction<Integer, Integer, Integer> gcd→ ⟨Block lambda D⟩ = (a, b) -> {41 int temp;42 while (b != 0) {43 temp = b;44 b = a % b;45 a = temp;46 }47 return a;48};4950System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));output classify(7): positive odd Local variables:return a;
46 }47 return a;48};System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));
50System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));output gcd(48, 18) = 6return a;
46 }47 return a;48};isValidPassword ← ⟨Block lambda E⟩, passwordToCheck ← abc123def
50System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));5253System.out.println("\nValidation:");5455Function<String, Boolean> isValidPassword→ ⟨Block lambda E⟩ = password -> {56 if (password == null || password.length() < 8) {57 return false;58 }59 60 boolean hasDigit = false;61 boolean hasLetter = false;62 63 for (char c : password.toCharArray()) {64 if (Character.isDigit(c)) hasDigit = true;65 if (Character.isLetter(c)) hasLetter = true;66 }67 68 return hasDigit && hasLetter;69};7071String passwordToCheck→ abc123def = "abc123def"; //@passwordToCheck="abc123def", "short", "onlyletters"72System.out.println(" '" + passwordToCheckabc123def + "' valid: " +73 isValidPassword.apply(passwordToCheckabc123def));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));output gcd(100, 35) = 5 Validation:return hasDigit && hasLetter;
68 return hasDigit && hasLetter;69};System.out.println(" '" + passwordToCheck + "' valid: " +
71String passwordToCheck = "abc123def"; //@passwordToCheck="abc123def", "short", "onlyletters"72System.out.println(" '" + passwordToCheckabc123def + "' valid: " +73 isValidPassword.apply(passwordToCheckabc123def));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));output 'abc123def' valid: trueSystem.out.println(" 'short' valid: " + isValidPassword.apply("short"…
73 isValidPassword.apply(passwordToCheck));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));output 'short' valid: falsereturn hasDigit && hasLetter;
68 return hasDigit && hasLetter;69};average ← ⟨Block lambda F⟩, scores ← [85, 90, 78, 92, 88]
74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));7677System.out.println("\nMulti-step processing:");7879Function<List<Integer>, Double> average→ ⟨Block lambda F⟩ = list -> {80 if (list.isEmpty()) {81 return 0.0;82 }83 84 int sum = 0;85 for (int n : list) {86 sum += n;87 }88 89 return (double) sum / list.size();90};9192List<Integer> scores→ [85, 90, 78, 92, 88] = Arrays.asList(85, 90, 78, 92, 88);93System.out.println(" Average score: " + average.apply(scores[85, 90, 78, 92, 88]));output 'onlyletters' valid: false Multi-step processing:return (double) sum / list.size();
89 return (double) sum / list.size();90};safeDivide ← ⟨Block lambda G⟩
92List<Integer> scores = Arrays.asList(85, 90, 78, 92, 88);93System.out.println(" Average score: " + average.apply(scores[85, 90, 78, 92, 88]));9495System.out.println("\nException handling:");9697BiFunction<Integer, Integer, Integer> safeDivide→ ⟨Block lambda G⟩ = (a, b) -> {98 try {99 return a / b;100 } catch (ArithmeticException e) {101 System.out.println(" Error: " + e.getMessage());102 return 0;103 }104};105106System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));output Average score: 86.6 Exception handling:System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));
106 System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107 System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));108}output 10 / 2 = 5catch (ArithmeticException e)
99 return a / b;100} catch (ArithmeticException e) {101 System.out.println(" Error: " + e.getMessage());102 return 0;103}output Error: / by zeroSystem.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));
106 System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107 System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));108}output 10 / 0 = 0
single ← ⟨Block lambda A⟩, block ← ⟨Block lambda B⟩
4public class Block {5 public static void main(String[] args) {6 System.out.println("Single vs block:\n");7 8 Function<Integer, Integer> single→ ⟨Block lambda A⟩ = x -> x * 2;9 10 Function<Integer, Integer> block→ ⟨Block lambda B⟩ = x -> {11 int result = x * 2;12 return result;13 };14 15 System.out.println(" Single: " + single.apply(5));16 System.out.println(" Block: " + block.apply(5));outputSingle vs block: Single: 10classify ← ⟨Block lambda C⟩
15System.out.println(" Single: " + single.apply(5));16System.out.println(" Block: " + block.apply(5));171819System.out.println("\nComplex logic:");2021Function<Integer, String> classify→ ⟨Block lambda C⟩ = n -> {22 if (n < 0) {23 return "negative";24 } else if (n == 0) {25 return "zero";26 } else if (n % 2 == 0) {27 return "positive even";28 } else {29 return "positive odd";30 }31};3233System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));output Block: 10 Complex logic:System.out.println(" classify(-5): " + classify.apply(-5));
33System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));output classify(-5): negativeSystem.out.println(" classify(0): " + classify.apply(0));
33System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));output classify(0): zeroSystem.out.println(" classify(4): " + classify.apply(4));
34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));output classify(4): positive evengcd ← ⟨Block lambda D⟩
35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));3738System.out.println("\nLocal variables:");3940BiFunction<Integer, Integer, Integer> gcd→ ⟨Block lambda D⟩ = (a, b) -> {41 int temp;42 while (b != 0) {43 temp = b;44 b = a % b;45 a = temp;46 }47 return a;48};4950System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));output classify(7): positive odd Local variables:return a;
46 }47 return a;48};System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));
50System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));output gcd(48, 18) = 6return a;
46 }47 return a;48};isValidPassword ← ⟨Block lambda E⟩, passwordToCheck ← short
50System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));5253System.out.println("\nValidation:");5455Function<String, Boolean> isValidPassword→ ⟨Block lambda E⟩ = password -> {56 if (password == null || password.length() < 8) {57 return false;58 }59 60 boolean hasDigit = false;61 boolean hasLetter = false;62 63 for (char c : password.toCharArray()) {64 if (Character.isDigit(c)) hasDigit = true;65 if (Character.isLetter(c)) hasLetter = true;66 }67 68 return hasDigit && hasLetter;69};7071String passwordToCheck→ short = "short";72System.out.println(" '" + passwordToCheckshort + "' valid: " +73 isValidPassword.apply(passwordToCheckshort));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));output gcd(100, 35) = 5 Validation:System.out.println(" '" + passwordToCheck + "' valid: " +
71String passwordToCheck = "short";72System.out.println(" '" + passwordToCheckshort + "' valid: " +73 isValidPassword.apply(passwordToCheckshort));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));output 'short' valid: falseSystem.out.println(" 'short' valid: " + isValidPassword.apply("short"…
73 isValidPassword.apply(passwordToCheck));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));output 'short' valid: falsereturn hasDigit && hasLetter;
68 return hasDigit && hasLetter;69};average ← ⟨Block lambda F⟩, scores ← [85, 90, 78, 92, 88]
74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));7677System.out.println("\nMulti-step processing:");7879Function<List<Integer>, Double> average→ ⟨Block lambda F⟩ = list -> {80 if (list.isEmpty()) {81 return 0.0;82 }83 84 int sum = 0;85 for (int n : list) {86 sum += n;87 }88 89 return (double) sum / list.size();90};9192List<Integer> scores→ [85, 90, 78, 92, 88] = Arrays.asList(85, 90, 78, 92, 88);93System.out.println(" Average score: " + average.apply(scores[85, 90, 78, 92, 88]));output 'onlyletters' valid: false Multi-step processing:return (double) sum / list.size();
89 return (double) sum / list.size();90};safeDivide ← ⟨Block lambda G⟩
92List<Integer> scores = Arrays.asList(85, 90, 78, 92, 88);93System.out.println(" Average score: " + average.apply(scores[85, 90, 78, 92, 88]));9495System.out.println("\nException handling:");9697BiFunction<Integer, Integer, Integer> safeDivide→ ⟨Block lambda G⟩ = (a, b) -> {98 try {99 return a / b;100 } catch (ArithmeticException e) {101 System.out.println(" Error: " + e.getMessage());102 return 0;103 }104};105106System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));output Average score: 86.6 Exception handling:System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));
106 System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107 System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));108}output 10 / 2 = 5catch (ArithmeticException e)
99 return a / b;100} catch (ArithmeticException e) {101 System.out.println(" Error: " + e.getMessage());102 return 0;103}output Error: / by zeroSystem.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));
106 System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107 System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));108}output 10 / 0 = 0
single ← ⟨Block lambda A⟩, block ← ⟨Block lambda B⟩
4public class Block {5 public static void main(String[] args) {6 System.out.println("Single vs block:\n");7 8 Function<Integer, Integer> single→ ⟨Block lambda A⟩ = x -> x * 2;9 10 Function<Integer, Integer> block→ ⟨Block lambda B⟩ = x -> {11 int result = x * 2;12 return result;13 };14 15 System.out.println(" Single: " + single.apply(5));16 System.out.println(" Block: " + block.apply(5));outputSingle vs block: Single: 10classify ← ⟨Block lambda C⟩
15System.out.println(" Single: " + single.apply(5));16System.out.println(" Block: " + block.apply(5));171819System.out.println("\nComplex logic:");2021Function<Integer, String> classify→ ⟨Block lambda C⟩ = n -> {22 if (n < 0) {23 return "negative";24 } else if (n == 0) {25 return "zero";26 } else if (n % 2 == 0) {27 return "positive even";28 } else {29 return "positive odd";30 }31};3233System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));output Block: 10 Complex logic:System.out.println(" classify(-5): " + classify.apply(-5));
33System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));output classify(-5): negativeSystem.out.println(" classify(0): " + classify.apply(0));
33System.out.println(" classify(-5): " + classify.apply(-5));34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));output classify(0): zeroSystem.out.println(" classify(4): " + classify.apply(4));
34System.out.println(" classify(0): " + classify.apply(0));35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));output classify(4): positive evengcd ← ⟨Block lambda D⟩
35System.out.println(" classify(4): " + classify.apply(4));36System.out.println(" classify(7): " + classify.apply(7));3738System.out.println("\nLocal variables:");3940BiFunction<Integer, Integer, Integer> gcd→ ⟨Block lambda D⟩ = (a, b) -> {41 int temp;42 while (b != 0) {43 temp = b;44 b = a % b;45 a = temp;46 }47 return a;48};4950System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));output classify(7): positive odd Local variables:return a;
46 }47 return a;48};System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));
50System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));output gcd(48, 18) = 6return a;
46 }47 return a;48};isValidPassword ← ⟨Block lambda E⟩, passwordToCheck ← onlyletters
50System.out.println(" gcd(48, 18) = " + gcd.apply(48, 18));51System.out.println(" gcd(100, 35) = " + gcd.apply(100, 35));5253System.out.println("\nValidation:");5455Function<String, Boolean> isValidPassword→ ⟨Block lambda E⟩ = password -> {56 if (password == null || password.length() < 8) {57 return false;58 }59 60 boolean hasDigit = false;61 boolean hasLetter = false;62 63 for (char c : password.toCharArray()) {64 if (Character.isDigit(c)) hasDigit = true;65 if (Character.isLetter(c)) hasLetter = true;66 }67 68 return hasDigit && hasLetter;69};7071String passwordToCheck→ onlyletters = "onlyletters";72System.out.println(" '" + passwordToCheckonlyletters + "' valid: " +73 isValidPassword.apply(passwordToCheckonlyletters));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));output gcd(100, 35) = 5 Validation:return hasDigit && hasLetter;
68 return hasDigit && hasLetter;69};System.out.println(" '" + passwordToCheck + "' valid: " +
71String passwordToCheck = "onlyletters";72System.out.println(" '" + passwordToCheckonlyletters + "' valid: " +73 isValidPassword.apply(passwordToCheckonlyletters));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));output 'onlyletters' valid: falseSystem.out.println(" 'short' valid: " + isValidPassword.apply("short"…
73 isValidPassword.apply(passwordToCheck));74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));output 'short' valid: falsereturn hasDigit && hasLetter;
68 return hasDigit && hasLetter;69};average ← ⟨Block lambda F⟩, scores ← [85, 90, 78, 92, 88]
74System.out.println(" 'short' valid: " + isValidPassword.apply("short"));75System.out.println(" 'onlyletters' valid: " + isValidPassword.apply("onlyletters"));7677System.out.println("\nMulti-step processing:");7879Function<List<Integer>, Double> average→ ⟨Block lambda F⟩ = list -> {80 if (list.isEmpty()) {81 return 0.0;82 }83 84 int sum = 0;85 for (int n : list) {86 sum += n;87 }88 89 return (double) sum / list.size();90};9192List<Integer> scores→ [85, 90, 78, 92, 88] = Arrays.asList(85, 90, 78, 92, 88);93System.out.println(" Average score: " + average.apply(scores[85, 90, 78, 92, 88]));output 'onlyletters' valid: false Multi-step processing:return (double) sum / list.size();
89 return (double) sum / list.size();90};safeDivide ← ⟨Block lambda G⟩
92List<Integer> scores = Arrays.asList(85, 90, 78, 92, 88);93System.out.println(" Average score: " + average.apply(scores[85, 90, 78, 92, 88]));9495System.out.println("\nException handling:");9697BiFunction<Integer, Integer, Integer> safeDivide→ ⟨Block lambda G⟩ = (a, b) -> {98 try {99 return a / b;100 } catch (ArithmeticException e) {101 System.out.println(" Error: " + e.getMessage());102 return 0;103 }104};105106System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));output Average score: 86.6 Exception handling:System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));
106 System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107 System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));108}output 10 / 2 = 5catch (ArithmeticException e)
99 return a / b;100} catch (ArithmeticException e) {101 System.out.println(" Error: " + e.getMessage());102 return 0;103}output Error: / by zeroSystem.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));
106 System.out.println(" 10 / 2 = " + safeDivide.apply(10, 2));107 System.out.println(" 10 / 0 = " + safeDivide.apply(10, 0));108}output 10 / 0 = 0
(x) -> { statements; return value; } - braces and return for complex logic.
Effectively final
Lambda can access local variables if effectively final.
EffectivelyFinal.java
Replay: real traced execution (multi-file project)
import java.util.*;
import java.util.function.*;
public class EffectivelyFinal {
public static void main(String[] args) {
System.out.println("Effectively final:\n");
int multiplier = 10;
Function<Integer, Integer> multiply = x -> x * multiplier;
System.out.println(" 5 * 10 = " + multiply.apply(5));
System.out.println(" 7 * 10 = " + multiply.apply(7));
System.out.println("\nMultiple captures:");
String prefix = "Value: ";
String suffix = "!";
Function<Integer, String> format = n -> prefix + n + suffix;
System.out.println(" " + format.apply(42));
System.out.println(" " + format.apply(99));
System.out.println("\nMethod parameters:");
processList(Arrays.asList(1, 2, 3, 4, 5), 3);
System.out.println("\nInstance variables:");
Counter counter = new Counter();
counter.demonstrate();
System.out.println("\nExplicit final:");
final int factor = 5;
BinaryOperator<Integer> scale = (a, b) -> (a + b) * factor;
System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));
System.out.println("\nArray capture:");
int[] counters = {0}; // Effectively final reference, mutable content
Runnable increment = () -> counters[0]++;
increment.run();
increment.run();
increment.run();
System.out.println(" Counter: " + counters[0]);
}
static void processList(List<Integer> numbers, int threshold) {
numbers.forEach(n -> {
if (n > threshold) {
System.out.println(" " + n + " exceeds " + threshold);
}
});
}
}
class Counter {
private int count = 0;
void demonstrate() {
Runnable inc = () -> count++;
inc.run();
inc.run();
inc.run();
System.out.println(" Count: " + count);
Supplier<Integer> getCount = () -> this.count;
System.out.println(" Get count: " + getCount.get());
}
}
import java.util.*;
import java.util.function.*;
public class EffectivelyFinal {
public static void main(String[] args) {
System.out.println("Effectively final:\n");
int multiplier = 3;
Function<Integer, Integer> multiply = x -> x * multiplier;
System.out.println(" 5 * 10 = " + multiply.apply(5));
System.out.println(" 7 * 10 = " + multiply.apply(7));
System.out.println("\nMultiple captures:");
String prefix = "Value: ";
String suffix = "!";
Function<Integer, String> format = n -> prefix + n + suffix;
System.out.println(" " + format.apply(42));
System.out.println(" " + format.apply(99));
System.out.println("\nMethod parameters:");
processList(Arrays.asList(1, 2, 3, 4, 5), 3);
System.out.println("\nInstance variables:");
Counter counter = new Counter();
counter.demonstrate();
System.out.println("\nExplicit final:");
final int factor = 5;
BinaryOperator<Integer> scale = (a, b) -> (a + b) * factor;
System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));
System.out.println("\nArray capture:");
int[] counters = {0}; // Effectively final reference, mutable content
Runnable increment = () -> counters[0]++;
increment.run();
increment.run();
increment.run();
System.out.println(" Counter: " + counters[0]);
}
static void processList(List<Integer> numbers, int threshold) {
numbers.forEach(n -> {
if (n > threshold) {
System.out.println(" " + n + " exceeds " + threshold);
}
});
}
}
class Counter {
private int count = 0;
void demonstrate() {
Runnable inc = () -> count++;
inc.run();
inc.run();
inc.run();
System.out.println(" Count: " + count);
Supplier<Integer> getCount = () -> this.count;
System.out.println(" Get count: " + getCount.get());
}
}
import java.util.*;
import java.util.function.*;
public class EffectivelyFinal {
public static void main(String[] args) {
System.out.println("Effectively final:\n");
int multiplier = 20;
Function<Integer, Integer> multiply = x -> x * multiplier;
System.out.println(" 5 * 10 = " + multiply.apply(5));
System.out.println(" 7 * 10 = " + multiply.apply(7));
System.out.println("\nMultiple captures:");
String prefix = "Value: ";
String suffix = "!";
Function<Integer, String> format = n -> prefix + n + suffix;
System.out.println(" " + format.apply(42));
System.out.println(" " + format.apply(99));
System.out.println("\nMethod parameters:");
processList(Arrays.asList(1, 2, 3, 4, 5), 3);
System.out.println("\nInstance variables:");
Counter counter = new Counter();
counter.demonstrate();
System.out.println("\nExplicit final:");
final int factor = 5;
BinaryOperator<Integer> scale = (a, b) -> (a + b) * factor;
System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));
System.out.println("\nArray capture:");
int[] counters = {0}; // Effectively final reference, mutable content
Runnable increment = () -> counters[0]++;
increment.run();
increment.run();
increment.run();
System.out.println(" Counter: " + counters[0]);
}
static void processList(List<Integer> numbers, int threshold) {
numbers.forEach(n -> {
if (n > threshold) {
System.out.println(" " + n + " exceeds " + threshold);
}
});
}
}
class Counter {
private int count = 0;
void demonstrate() {
Runnable inc = () -> count++;
inc.run();
inc.run();
inc.run();
System.out.println(" Count: " + count);
Supplier<Integer> getCount = () -> this.count;
System.out.println(" Get count: " + getCount.get());
}
}
multiplier ← 10, multiply ← ⟨EffectivelyFinal lambda A⟩, prefix ← Value:
4public class EffectivelyFinal {5 public static void main(String[] args) {6 System.out.println("Effectively final:\n");7 8 int multiplier→ 10 = 10; //@multiplier=10, 3, 209 10 Function<Integer, Integer> multiply→ ⟨EffectivelyFinal lambda A⟩ = x -> x * multiplier;11 12 System.out.println(" 5 * 10 = " + multiply.apply(5));13 System.out.println(" 7 * 10 = " + multiply.apply(7));14 15 16 17 System.out.println("\nMultiple captures:");18 19 String prefix→ Value: = "Value: ";20 String suffix→ ! = "!";21 22 Function<Integer, String> format→ ⟨EffectivelyFinal lambda B⟩ = n -> prefix + n + suffix;23 24 System.out.println(" " + format.apply(42));25 System.out.println(" " + format.apply(99));26 27 System.out.println("\nMethod parameters:");28 29 processList(Arrays.asList(1, 2, 3, 4, 5), 3);outputEffectively final: 5 * 10 = 50 7 * 10 = 70 Multiple captures: Value: 42! Value: 99! Method parameters:static void processList(List<Integer> numbers, int threshold)
57static void processList(List<Integer> numbers[1, 2, 3, 4, 5], int threshold3) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63}n ->
pass 1 of 557static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {All 5 passes — pass 1 is the card above pass countcounters[0]counterincgetCountfactorscaleincrement1 — — — — — — — — 2 — — — — — — — — 3 — — — — — — — — 4 — — — — — — — — 5 3 3 ⟨Counter C⟩ ⟨Counter lambda D⟩ ⟨Counter lambda E⟩ 5 ⟨EffectivelyFinal lambda F⟩ ⟨EffectivelyFinal lambda G⟩ if (n > threshold)
pass 1 of 258numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }output 4 exceeds 3counter ← ⟨Counter C⟩
pass 2 of 229 processList(Arrays.asList(1, 2, 3, 4, 5), 3);30 31 System.out.println("\nInstance variables:");32 33 Counter counter→ ⟨Counter C⟩ = new Counter();34 counter.demonstrate();35 36 System.out.println("\nExplicit final:");37 38 final int factor = 5;39 40 BinaryOperator<Integer> scale = (a, b) -> (a + b) * factor;41 42 System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));43 44 System.out.println("\nArray capture:");45 46 int[] counters = {0}; // Effectively final reference, mutable content47 48 Runnable increment = () -> counters[0]++;49 50 increment.run();51 increment.run();52 increment.run();53 54 System.out.println(" Counter: " + counters[0]);55}5657static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63}output 5 exceeds 3 Instance variables:inc ← ⟨Counter lambda D⟩, getCount ← ⟨Counter lambda E⟩, factor ← 5
33 Counter counter = new Counter();34 counter.demonstrate();35 36 System.out.println("\nExplicit final:");37 38 final int factor→ 5 = 5;39 40 BinaryOperator<Integer> scale→ ⟨EffectivelyFinal lambda F⟩ = (a, b) -> (a + b) * factor;41 42 System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));43 44 System.out.println("\nArray capture:");45 46 int[] counters = {0}; // Effectively final reference, mutable content47 48 Runnable increment→ ⟨EffectivelyFinal lambda G⟩ = () -> counters[0]++;49 50 increment.run();51 increment.run();52 increment.run();53 54 System.out.println(" Counter: " + counters[0]3);55 }56 57 static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63 }64}6566class Counter {67 private int count = 0;68 69 void demonstrate() {70 Runnable inc→ ⟨Counter lambda D⟩ = () -> count++;71 72 inc.run();73 inc.run();74 inc.run();75 76 System.out.println(" Count: " + count3);77 78 Supplier<Integer> getCount→ ⟨Counter lambda E⟩ = () -> this.count;79 System.out.println(" Get count: " + getCount.get());80 }output Count: 3 Get count: 3 Explicit final: (2 + 3) * 5 = 25 Array capture: Counter: 3
multiplier ← 3, multiply ← ⟨EffectivelyFinal lambda A⟩, prefix ← Value:
4public class EffectivelyFinal {5 public static void main(String[] args) {6 System.out.println("Effectively final:\n");7 8 int multiplier→ 3 = 3;9 10 Function<Integer, Integer> multiply→ ⟨EffectivelyFinal lambda A⟩ = x -> x * multiplier;11 12 System.out.println(" 5 * 10 = " + multiply.apply(5));13 System.out.println(" 7 * 10 = " + multiply.apply(7));14 15 16 17 System.out.println("\nMultiple captures:");18 19 String prefix→ Value: = "Value: ";20 String suffix→ ! = "!";21 22 Function<Integer, String> format→ ⟨EffectivelyFinal lambda B⟩ = n -> prefix + n + suffix;23 24 System.out.println(" " + format.apply(42));25 System.out.println(" " + format.apply(99));26 27 System.out.println("\nMethod parameters:");28 29 processList(Arrays.asList(1, 2, 3, 4, 5), 3);outputEffectively final: 5 * 10 = 15 7 * 10 = 21 Multiple captures: Value: 42! Value: 99! Method parameters:static void processList(List<Integer> numbers, int threshold)
57static void processList(List<Integer> numbers[1, 2, 3, 4, 5], int threshold3) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63}n ->
pass 1 of 557static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {All 5 passes — pass 1 is the card above pass countcounters[0]counterincgetCountfactorscaleincrement1 — — — — — — — — 2 — — — — — — — — 3 — — — — — — — — 4 — — — — — — — — 5 3 3 ⟨Counter C⟩ ⟨Counter lambda D⟩ ⟨Counter lambda E⟩ 5 ⟨EffectivelyFinal lambda F⟩ ⟨EffectivelyFinal lambda G⟩ if (n > threshold)
pass 1 of 258numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }output 4 exceeds 3counter ← ⟨Counter C⟩
pass 2 of 229 processList(Arrays.asList(1, 2, 3, 4, 5), 3);30 31 System.out.println("\nInstance variables:");32 33 Counter counter→ ⟨Counter C⟩ = new Counter();34 counter.demonstrate();35 36 System.out.println("\nExplicit final:");37 38 final int factor = 5;39 40 BinaryOperator<Integer> scale = (a, b) -> (a + b) * factor;41 42 System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));43 44 System.out.println("\nArray capture:");45 46 int[] counters = {0}; // Effectively final reference, mutable content47 48 Runnable increment = () -> counters[0]++;49 50 increment.run();51 increment.run();52 increment.run();53 54 System.out.println(" Counter: " + counters[0]);55}5657static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63}output 5 exceeds 3 Instance variables:inc ← ⟨Counter lambda D⟩, getCount ← ⟨Counter lambda E⟩, factor ← 5
33 Counter counter = new Counter();34 counter.demonstrate();35 36 System.out.println("\nExplicit final:");37 38 final int factor→ 5 = 5;39 40 BinaryOperator<Integer> scale→ ⟨EffectivelyFinal lambda F⟩ = (a, b) -> (a + b) * factor;41 42 System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));43 44 System.out.println("\nArray capture:");45 46 int[] counters = {0}; // Effectively final reference, mutable content47 48 Runnable increment→ ⟨EffectivelyFinal lambda G⟩ = () -> counters[0]++;49 50 increment.run();51 increment.run();52 increment.run();53 54 System.out.println(" Counter: " + counters[0]3);55 }56 57 static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63 }64}6566class Counter {67 private int count = 0;68 69 void demonstrate() {70 Runnable inc→ ⟨Counter lambda D⟩ = () -> count++;71 72 inc.run();73 inc.run();74 inc.run();75 76 System.out.println(" Count: " + count3);77 78 Supplier<Integer> getCount→ ⟨Counter lambda E⟩ = () -> this.count;79 System.out.println(" Get count: " + getCount.get());80 }output Count: 3 Get count: 3 Explicit final: (2 + 3) * 5 = 25 Array capture: Counter: 3
multiplier ← 20, multiply ← ⟨EffectivelyFinal lambda A⟩, prefix ← Value:
4public class EffectivelyFinal {5 public static void main(String[] args) {6 System.out.println("Effectively final:\n");7 8 int multiplier→ 20 = 20;9 10 Function<Integer, Integer> multiply→ ⟨EffectivelyFinal lambda A⟩ = x -> x * multiplier;11 12 System.out.println(" 5 * 10 = " + multiply.apply(5));13 System.out.println(" 7 * 10 = " + multiply.apply(7));14 15 16 17 System.out.println("\nMultiple captures:");18 19 String prefix→ Value: = "Value: ";20 String suffix→ ! = "!";21 22 Function<Integer, String> format→ ⟨EffectivelyFinal lambda B⟩ = n -> prefix + n + suffix;23 24 System.out.println(" " + format.apply(42));25 System.out.println(" " + format.apply(99));26 27 System.out.println("\nMethod parameters:");28 29 processList(Arrays.asList(1, 2, 3, 4, 5), 3);outputEffectively final: 5 * 10 = 100 7 * 10 = 140 Multiple captures: Value: 42! Value: 99! Method parameters:static void processList(List<Integer> numbers, int threshold)
57static void processList(List<Integer> numbers[1, 2, 3, 4, 5], int threshold3) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63}n ->
pass 1 of 557static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {All 5 passes — pass 1 is the card above pass countcounters[0]counterincgetCountfactorscaleincrement1 — — — — — — — — 2 — — — — — — — — 3 — — — — — — — — 4 — — — — — — — — 5 3 3 ⟨Counter C⟩ ⟨Counter lambda D⟩ ⟨Counter lambda E⟩ 5 ⟨EffectivelyFinal lambda F⟩ ⟨EffectivelyFinal lambda G⟩ if (n > threshold)
pass 1 of 258numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }output 4 exceeds 3counter ← ⟨Counter C⟩
pass 2 of 229 processList(Arrays.asList(1, 2, 3, 4, 5), 3);30 31 System.out.println("\nInstance variables:");32 33 Counter counter→ ⟨Counter C⟩ = new Counter();34 counter.demonstrate();35 36 System.out.println("\nExplicit final:");37 38 final int factor = 5;39 40 BinaryOperator<Integer> scale = (a, b) -> (a + b) * factor;41 42 System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));43 44 System.out.println("\nArray capture:");45 46 int[] counters = {0}; // Effectively final reference, mutable content47 48 Runnable increment = () -> counters[0]++;49 50 increment.run();51 increment.run();52 increment.run();53 54 System.out.println(" Counter: " + counters[0]);55}5657static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63}output 5 exceeds 3 Instance variables:inc ← ⟨Counter lambda D⟩, getCount ← ⟨Counter lambda E⟩, factor ← 5
33 Counter counter = new Counter();34 counter.demonstrate();35 36 System.out.println("\nExplicit final:");37 38 final int factor→ 5 = 5;39 40 BinaryOperator<Integer> scale→ ⟨EffectivelyFinal lambda F⟩ = (a, b) -> (a + b) * factor;41 42 System.out.println(" (2 + 3) * 5 = " + scale.apply(2, 3));43 44 System.out.println("\nArray capture:");45 46 int[] counters = {0}; // Effectively final reference, mutable content47 48 Runnable increment→ ⟨EffectivelyFinal lambda G⟩ = () -> counters[0]++;49 50 increment.run();51 increment.run();52 increment.run();53 54 System.out.println(" Counter: " + counters[0]3);55 }56 57 static void processList(List<Integer> numbers, int threshold) {58 numbers.forEach(n -> {59 if (n > threshold) {60 System.out.println(" " + n + " exceeds " + threshold);61 }62 });63 }64}6566class Counter {67 private int count = 0;68 69 void demonstrate() {70 Runnable inc→ ⟨Counter lambda D⟩ = () -> count++;71 72 inc.run();73 inc.run();74 inc.run();75 76 System.out.println(" Count: " + count3);77 78 Supplier<Integer> getCount→ ⟨Counter lambda E⟩ = () -> this.count;79 System.out.println(" Get count: " + getCount.get());80 }output Count: 3 Get count: 3 Explicit final: (2 + 3) * 5 = 25 Array capture: Counter: 3
Variables accessed in lambda can't be modified. Effectively final = never reassigned.
effectively final
Variable never reassigned after initialization. Required for lambda capture.
Common use cases
Where lambdas shine.
UseCases.java
Replay: real traced execution (multi-file project)
import java.util.*;
import java.util.function.*;
public class UseCases {
public static void main(String[] args) {
System.out.println("Thread creation:\n");
Thread oldThread = new Thread(new Runnable() {
@Override
public void run() {
System.out.println(" Old way thread");
}
});
Thread newThread = new Thread(() -> {
System.out.println(" Lambda thread");
});
try {
oldThread.start();
oldThread.join();
newThread.start();
newThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("\nSorting:");
List<String> names = new ArrayList<>(
Arrays.asList("Charlie", "Alice", "Bob", "David"));
names.sort((a, b) -> a.compareTo(b));
System.out.println(" By name: " + names);
names.sort((a, b) -> Integer.compare(a.length(), b.length()));
System.out.println(" By length: " + names);
names.sort((a, b) -> {
char lastA = a.charAt(a.length() - 1);
char lastB = b.charAt(b.length() - 1);
return Character.compare(lastA, lastB);
});
System.out.println(" By last char: " + names);
System.out.println("\nList processing:");
List<Integer> numbers = new ArrayList<>(
Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
System.out.print(" All: ");
numbers.forEach(n -> System.out.print(n + " "));
System.out.println();
numbers.removeIf(n -> n % 2 == 0);
System.out.println(" After removing evens: " + numbers);
numbers.replaceAll(n -> n * 10);
System.out.println(" After * 10: " + numbers);
System.out.println("\nMap operations:");
Map<String, Integer> scores = new LinkedHashMap<>();
scores.put("Alice", 85);
scores.put("Bob", 92);
scores.put("Charlie", 78);
scores.forEach((name, score) ->
System.out.println(" " + name + ": " + score));
scores.replaceAll((name, score) -> score + 5); // Curve grades
System.out.println(" After curve: " + scores);
scores.computeIfAbsent("David", k -> 80);
System.out.println(" After adding David: " + scores);
System.out.println("\nCustom callbacks:");
processData(Arrays.asList(1, 2, 3, 4, 5),
n -> n * 2,
n -> System.out.println(" Processed: " + n)
);
System.out.println("\nEvent handlers:");
Button button = new Button("Click me");
button.setOnClick(() -> System.out.println(" Button clicked!"));
button.setOnClick(() -> System.out.println(" Action performed"));
button.click();
System.out.println("\nConditional logic:");
List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
int cutoff = 5;
filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);
filterAndPrint(values, n -> n % 2 == 0, "Even numbers");
filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");
}
static void processData(List<Integer> data,
Function<Integer, Integer> processor,
Consumer<Integer> outputter) {
for (Integer item : data) {
Integer processed = processor.apply(item);
outputter.accept(processed);
}
}
static void filterAndPrint(List<Integer> list,
Predicate<Integer> filter,
String label) {
System.out.print(" " + label + ": ");
list.stream()
.filter(filter)
.forEach(n -> System.out.print(n + " "));
System.out.println();
}
}
class Button {
private String text;
private Runnable onClick;
Button(String text) {
this.text = text;
}
void setOnClick(Runnable action) {
this.onClick = action;
}
void click() {
if (onClick != null) {
onClick.run();
}
}
}
import java.util.*;
import java.util.function.*;
public class UseCases {
public static void main(String[] args) {
System.out.println("Thread creation:\n");
Thread oldThread = new Thread(new Runnable() {
@Override
public void run() {
System.out.println(" Old way thread");
}
});
Thread newThread = new Thread(() -> {
System.out.println(" Lambda thread");
});
try {
oldThread.start();
oldThread.join();
newThread.start();
newThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("\nSorting:");
List<String> names = new ArrayList<>(
Arrays.asList("Charlie", "Alice", "Bob", "David"));
names.sort((a, b) -> a.compareTo(b));
System.out.println(" By name: " + names);
names.sort((a, b) -> Integer.compare(a.length(), b.length()));
System.out.println(" By length: " + names);
names.sort((a, b) -> {
char lastA = a.charAt(a.length() - 1);
char lastB = b.charAt(b.length() - 1);
return Character.compare(lastA, lastB);
});
System.out.println(" By last char: " + names);
System.out.println("\nList processing:");
List<Integer> numbers = new ArrayList<>(
Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
System.out.print(" All: ");
numbers.forEach(n -> System.out.print(n + " "));
System.out.println();
numbers.removeIf(n -> n % 2 == 0);
System.out.println(" After removing evens: " + numbers);
numbers.replaceAll(n -> n * 10);
System.out.println(" After * 10: " + numbers);
System.out.println("\nMap operations:");
Map<String, Integer> scores = new LinkedHashMap<>();
scores.put("Alice", 85);
scores.put("Bob", 92);
scores.put("Charlie", 78);
scores.forEach((name, score) ->
System.out.println(" " + name + ": " + score));
scores.replaceAll((name, score) -> score + 5); // Curve grades
System.out.println(" After curve: " + scores);
scores.computeIfAbsent("David", k -> 80);
System.out.println(" After adding David: " + scores);
System.out.println("\nCustom callbacks:");
processData(Arrays.asList(1, 2, 3, 4, 5),
n -> n * 2,
n -> System.out.println(" Processed: " + n)
);
System.out.println("\nEvent handlers:");
Button button = new Button("Click me");
button.setOnClick(() -> System.out.println(" Button clicked!"));
button.setOnClick(() -> System.out.println(" Action performed"));
button.click();
System.out.println("\nConditional logic:");
List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
int cutoff = 3;
filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);
filterAndPrint(values, n -> n % 2 == 0, "Even numbers");
filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");
}
static void processData(List<Integer> data,
Function<Integer, Integer> processor,
Consumer<Integer> outputter) {
for (Integer item : data) {
Integer processed = processor.apply(item);
outputter.accept(processed);
}
}
static void filterAndPrint(List<Integer> list,
Predicate<Integer> filter,
String label) {
System.out.print(" " + label + ": ");
list.stream()
.filter(filter)
.forEach(n -> System.out.print(n + " "));
System.out.println();
}
}
class Button {
private String text;
private Runnable onClick;
Button(String text) {
this.text = text;
}
void setOnClick(Runnable action) {
this.onClick = action;
}
void click() {
if (onClick != null) {
onClick.run();
}
}
}
import java.util.*;
import java.util.function.*;
public class UseCases {
public static void main(String[] args) {
System.out.println("Thread creation:\n");
Thread oldThread = new Thread(new Runnable() {
@Override
public void run() {
System.out.println(" Old way thread");
}
});
Thread newThread = new Thread(() -> {
System.out.println(" Lambda thread");
});
try {
oldThread.start();
oldThread.join();
newThread.start();
newThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("\nSorting:");
List<String> names = new ArrayList<>(
Arrays.asList("Charlie", "Alice", "Bob", "David"));
names.sort((a, b) -> a.compareTo(b));
System.out.println(" By name: " + names);
names.sort((a, b) -> Integer.compare(a.length(), b.length()));
System.out.println(" By length: " + names);
names.sort((a, b) -> {
char lastA = a.charAt(a.length() - 1);
char lastB = b.charAt(b.length() - 1);
return Character.compare(lastA, lastB);
});
System.out.println(" By last char: " + names);
System.out.println("\nList processing:");
List<Integer> numbers = new ArrayList<>(
Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
System.out.print(" All: ");
numbers.forEach(n -> System.out.print(n + " "));
System.out.println();
numbers.removeIf(n -> n % 2 == 0);
System.out.println(" After removing evens: " + numbers);
numbers.replaceAll(n -> n * 10);
System.out.println(" After * 10: " + numbers);
System.out.println("\nMap operations:");
Map<String, Integer> scores = new LinkedHashMap<>();
scores.put("Alice", 85);
scores.put("Bob", 92);
scores.put("Charlie", 78);
scores.forEach((name, score) ->
System.out.println(" " + name + ": " + score));
scores.replaceAll((name, score) -> score + 5); // Curve grades
System.out.println(" After curve: " + scores);
scores.computeIfAbsent("David", k -> 80);
System.out.println(" After adding David: " + scores);
System.out.println("\nCustom callbacks:");
processData(Arrays.asList(1, 2, 3, 4, 5),
n -> n * 2,
n -> System.out.println(" Processed: " + n)
);
System.out.println("\nEvent handlers:");
Button button = new Button("Click me");
button.setOnClick(() -> System.out.println(" Button clicked!"));
button.setOnClick(() -> System.out.println(" Action performed"));
button.click();
System.out.println("\nConditional logic:");
List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
int cutoff = 8;
filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);
filterAndPrint(values, n -> n % 2 == 0, "Even numbers");
filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");
}
static void processData(List<Integer> data,
Function<Integer, Integer> processor,
Consumer<Integer> outputter) {
for (Integer item : data) {
Integer processed = processor.apply(item);
outputter.accept(processed);
}
}
static void filterAndPrint(List<Integer> list,
Predicate<Integer> filter,
String label) {
System.out.print(" " + label + ": ");
list.stream()
.filter(filter)
.forEach(n -> System.out.print(n + " "));
System.out.println();
}
}
class Button {
private String text;
private Runnable onClick;
Button(String text) {
this.text = text;
}
void setOnClick(Runnable action) {
this.onClick = action;
}
void click() {
if (onClick != null) {
onClick.run();
}
}
}
oldThread ← Thread[#19,Thread-0,5,main], newThread ← Thread[#20,Thread-1,5,main]
4public class UseCases {5 public static void main(String[] args) {6 System.out.println("Thread creation:\n");7 8 Thread oldThread→ Thread[#19,Thread-0,5,main] = new Thread(new Runnable() {9 @Override10 public void run() {11 System.out.println(" Old way thread");12 }13 });14 15 Thread newThread→ Thread[#20,Thread-1,5,main] = new Thread(() -> {16 System.out.println(" Lambda thread");17 });outputThread creation:oldThread.join();
10 public void run() {11 System.out.println(" Old way thread");12 }13});1415Thread newThread = new Thread(() -> {16 System.out.println(" Lambda thread");17});1819try {20 oldThread.start();21 oldThread.join();22 newThread.start();23 newThread.join();24} catch (InterruptedException e) {output Old way thread() ->
15Thread newThread = new Thread(() -> {16 System.out.println(" Lambda thread");17});output Lambda threadnewThread.join();
22 newThread.start();23 newThread.join();24} catch (InterruptedException e) {names ← [Charlie, Alice, Bob, David], numbers ← [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
29System.out.println("\nSorting:");3031List<String> names→ [Charlie, Alice, Bob, David] = new ArrayList<>(32 Arrays.asList("Charlie", "Alice", "Bob", "David"));3334names.sort((a, b) -> a.compareTo(b));35System.out.println(" By name: " + names[Alice, Bob, Charlie, David]);3637names.sort((a, b) -> Integer.compare(a.length(), b.length()));38System.out.println(" By length: " + names[Bob, Alice, David, Charlie]);3940names.sort((a, b) -> {41 char lastA = a.charAt(a.length() - 1);42 char lastB = b.charAt(b.length() - 1);43 return Character.compare(lastA, lastB);44});45System.out.println(" By last char: " + names[Bob, David, Alice, Charlie]);4647System.out.println("\nList processing:");4849List<Integer> numbers→ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] = new ArrayList<>(50 Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));5152System.out.print(" All: ");53numbers.forEach(n -> System.out.print(n + " "));54System.out.println();5556numbers.removeIf(n -> n % 2 == 0);57System.out.println(" After removing evens: " + numbers[1, 3, 5, 7, 9]);5859numbers.replaceAll(n -> n * 10);60System.out.println(" After * 10: " + numbers[10, 30, 50, 70, 90]);6162System.out.println("\nMap operations:");6364Map<String, Integer> scores→ {} = new LinkedHashMap<>();65scores.put("Alice", 85);66scores.put("Bob", 92);67scores.put("Charlie", 78);6869scores.forEach((name, score) -> 70 System.out.println(" " + name + ": " + score));7172scores.replaceAll((name, score) -> score + 5); // Curve grades73System.out.println(" After curve: " + scores{Alice=90, Bob=97, Charlie=83});7475scores.computeIfAbsent("David", k -> 80);76System.out.println(" After adding David: " + scores{Alice=90, Bob=97, Charlie=83, David=80});7778System.out.println("\nCustom callbacks:");7980processData(Arrays.asList(1, 2, 3, 4, 5),81 n -> n * 2,82 n -> System.out.println(" Processed: " + n)83);output Sorting: By name: [Alice, Bob, Charlie, David] By length: [Bob, Alice, David, Charlie] By last char: [Bob, David, Alice, Charlie] List processing: All: After removing evens: [1, 3, 5, 7, 9] After * 10: [10, 30, 50, 70, 90] Map operations: After curve: {Alice=90, Bob=97, Charlie=83} After adding David: {Alice=90, Bob=97, Charlie=83, David=80} Custom callbacks:static void processData(List<Integer> data, …
104static void processData(List<Integer> data[1, 2, 3, 4, 5],105 Function<Integer, Integer> processor⟨UseCases lambda A⟩,106 Consumer<Integer> outputter⟨UseCases lambda B⟩) {107 for (Integer item : data) {processed ← 2
pass 1 of 5106 Consumer<Integer> outputter) {107for (Integer item1 : data[1, 2, 3, 4, 5]) {108 Integer processed→ 2 = processor.apply(item1);109 outputter.accept(processed2);110}All 5 passes — pass 1 is the card above pass itemtextactiononClickprocessedthis.textbuttonthis.onClickvaluescutoff1 1 — — — 2 — — — — — 2 2 — — — 4 — — — — — 3 3 — — — 6 — — — — — 4 4 — — — 8 — — — — — 5 5 Click me ⟨UseCases lambda C⟩ ⟨UseCases lambda D⟩ 10 Click me ⟨Button E⟩ ⟨UseCases lambda C⟩ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 5 this.text ← Click me, button ← ⟨Button E⟩
87 Button button→ ⟨Button E⟩ = new Button("Click me");88 89 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 5; //@cutoff=5, 3, 899 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String textClick me) {129 this.text→ Click me = textClick me;130 }this.onClick ← ⟨UseCases lambda C⟩
pass 1 of 289 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 5; //@cutoff=5, 3, 899 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action⟨UseCases lambda C⟩) {133 this.onClick→ ⟨UseCases lambda C⟩ = action⟨UseCases lambda C⟩;134 }this.onClick ← ⟨UseCases lambda D⟩
pass 2 of 289 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 5; //@cutoff=5, 3, 899 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action⟨UseCases lambda D⟩) {133 this.onClick→ ⟨UseCases lambda D⟩ = action⟨UseCases lambda D⟩;134 }values ← [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], cutoff ← 5
92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values→ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff→ 5 = 5; //@cutoff=5, 3, 899 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n > cutoff, "Greater than " + cutoff5);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action) {133 this.onClick = action;134 }135 136 void click() {137 if (onClick⟨UseCases lambda D⟩ != null) {138 onClick.run();139 }output Conditional logic:static void filterAndPrint(List<Integer> list, …
pass 1 of 398 int cutoff = 5; //@cutoff=5, 3, 899 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n > cutoff, "Greater than " + cutoff5);100 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102}103104static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111}112113static void filterAndPrint(List<Integer> list[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 114 Predicate<Integer> filter⟨UseCases lambda F⟩,115 String labelGreater than 5) {116 System.out.print(" " + labelGreater than 5 + ": ");117 list.stream()118 .filter(filter⟨UseCases lambda F⟩)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121}output Greater than 5:All 3 passes — pass 1 is the card above pass filterlabelcutoff1 ⟨UseCases lambda F⟩ Greater than 5 5 2 ⟨UseCases lambda G⟩ Even numbers — 3 ⟨UseCases lambda H⟩ Divisible by 3 —
oldThread ← Thread[#19,Thread-0,5,main], newThread ← Thread[#20,Thread-1,5,main]
4public class UseCases {5 public static void main(String[] args) {6 System.out.println("Thread creation:\n");7 8 Thread oldThread→ Thread[#19,Thread-0,5,main] = new Thread(new Runnable() {9 @Override10 public void run() {11 System.out.println(" Old way thread");12 }13 });14 15 Thread newThread→ Thread[#20,Thread-1,5,main] = new Thread(() -> {16 System.out.println(" Lambda thread");17 });outputThread creation:@Override public void run()
8Thread oldThread = new Thread(new Runnable() {9 @Override10 public void run() {11 System.out.println(" Old way thread");12 }output Old way threadoldThread.join();
20oldThread.start();21oldThread.join();22newThread.start();23newThread.join();newThread.join();
15Thread newThread = new Thread(() -> {16 System.out.println(" Lambda thread");17});1819try {20 oldThread.start();21 oldThread.join();22 newThread.start();23 newThread.join();24} catch (InterruptedException e) {output Lambda threadnames ← [Charlie, Alice, Bob, David], numbers ← [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
29System.out.println("\nSorting:");3031List<String> names→ [Charlie, Alice, Bob, David] = new ArrayList<>(32 Arrays.asList("Charlie", "Alice", "Bob", "David"));3334names.sort((a, b) -> a.compareTo(b));35System.out.println(" By name: " + names[Alice, Bob, Charlie, David]);3637names.sort((a, b) -> Integer.compare(a.length(), b.length()));38System.out.println(" By length: " + names[Bob, Alice, David, Charlie]);3940names.sort((a, b) -> {41 char lastA = a.charAt(a.length() - 1);42 char lastB = b.charAt(b.length() - 1);43 return Character.compare(lastA, lastB);44});45System.out.println(" By last char: " + names[Bob, David, Alice, Charlie]);4647System.out.println("\nList processing:");4849List<Integer> numbers→ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] = new ArrayList<>(50 Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));5152System.out.print(" All: ");53numbers.forEach(n -> System.out.print(n + " "));54System.out.println();5556numbers.removeIf(n -> n % 2 == 0);57System.out.println(" After removing evens: " + numbers[1, 3, 5, 7, 9]);5859numbers.replaceAll(n -> n * 10);60System.out.println(" After * 10: " + numbers[10, 30, 50, 70, 90]);6162System.out.println("\nMap operations:");6364Map<String, Integer> scores→ {} = new LinkedHashMap<>();65scores.put("Alice", 85);66scores.put("Bob", 92);67scores.put("Charlie", 78);6869scores.forEach((name, score) -> 70 System.out.println(" " + name + ": " + score));7172scores.replaceAll((name, score) -> score + 5); // Curve grades73System.out.println(" After curve: " + scores{Alice=90, Bob=97, Charlie=83});7475scores.computeIfAbsent("David", k -> 80);76System.out.println(" After adding David: " + scores{Alice=90, Bob=97, Charlie=83, David=80});7778System.out.println("\nCustom callbacks:");7980processData(Arrays.asList(1, 2, 3, 4, 5),81 n -> n * 2,82 n -> System.out.println(" Processed: " + n)83);output Sorting: By name: [Alice, Bob, Charlie, David] By length: [Bob, Alice, David, Charlie] By last char: [Bob, David, Alice, Charlie] List processing: All: After removing evens: [1, 3, 5, 7, 9] After * 10: [10, 30, 50, 70, 90] Map operations: After curve: {Alice=90, Bob=97, Charlie=83} After adding David: {Alice=90, Bob=97, Charlie=83, David=80} Custom callbacks:static void processData(List<Integer> data, …
104static void processData(List<Integer> data[1, 2, 3, 4, 5],105 Function<Integer, Integer> processor⟨UseCases lambda A⟩,106 Consumer<Integer> outputter⟨UseCases lambda B⟩) {107 for (Integer item : data) {processed ← 2
pass 1 of 5106 Consumer<Integer> outputter) {107for (Integer item1 : data[1, 2, 3, 4, 5]) {108 Integer processed→ 2 = processor.apply(item1);109 outputter.accept(processed2);110}All 5 passes — pass 1 is the card above pass itemtextactiononClickprocessedthis.textbuttonthis.onClickvaluescutoff1 1 — — — 2 — — — — — 2 2 — — — 4 — — — — — 3 3 — — — 6 — — — — — 4 4 — — — 8 — — — — — 5 5 Click me ⟨UseCases lambda C⟩ ⟨UseCases lambda D⟩ 10 Click me ⟨Button E⟩ ⟨UseCases lambda C⟩ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 3 this.text ← Click me, button ← ⟨Button E⟩
87 Button button→ ⟨Button E⟩ = new Button("Click me");88 89 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 3;99 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String textClick me) {129 this.text→ Click me = textClick me;130 }this.onClick ← ⟨UseCases lambda C⟩
pass 1 of 289 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 3;99 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action⟨UseCases lambda C⟩) {133 this.onClick→ ⟨UseCases lambda C⟩ = action⟨UseCases lambda C⟩;134 }this.onClick ← ⟨UseCases lambda D⟩
pass 2 of 289 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 3;99 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action⟨UseCases lambda D⟩) {133 this.onClick→ ⟨UseCases lambda D⟩ = action⟨UseCases lambda D⟩;134 }values ← [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], cutoff ← 3
92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values→ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff→ 3 = 3;99 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n > cutoff, "Greater than " + cutoff3);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action) {133 this.onClick = action;134 }135 136 void click() {137 if (onClick⟨UseCases lambda D⟩ != null) {138 onClick.run();139 }output Conditional logic:static void filterAndPrint(List<Integer> list, …
pass 1 of 398 int cutoff = 3;99 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n > cutoff, "Greater than " + cutoff3);100 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102}103104static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111}112113static void filterAndPrint(List<Integer> list[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 114 Predicate<Integer> filter⟨UseCases lambda F⟩,115 String labelGreater than 3) {116 System.out.print(" " + labelGreater than 3 + ": ");117 list.stream()118 .filter(filter⟨UseCases lambda F⟩)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121}output Greater than 3:All 3 passes — pass 1 is the card above pass filterlabelcutoff1 ⟨UseCases lambda F⟩ Greater than 3 3 2 ⟨UseCases lambda G⟩ Even numbers — 3 ⟨UseCases lambda H⟩ Divisible by 3 —
oldThread ← Thread[#19,Thread-0,5,main], newThread ← Thread[#20,Thread-1,5,main]
4public class UseCases {5 public static void main(String[] args) {6 System.out.println("Thread creation:\n");7 8 Thread oldThread→ Thread[#19,Thread-0,5,main] = new Thread(new Runnable() {9 @Override10 public void run() {11 System.out.println(" Old way thread");12 }13 });14 15 Thread newThread→ Thread[#20,Thread-1,5,main] = new Thread(() -> {16 System.out.println(" Lambda thread");17 });outputThread creation:@Override public void run()
8Thread oldThread = new Thread(new Runnable() {9 @Override10 public void run() {11 System.out.println(" Old way thread");12 }output Old way threadoldThread.join();
20 oldThread.start();21 oldThread.join();22 newThread.start();23 newThread.join();24} catch (InterruptedException e) {() ->
15Thread newThread = new Thread(() -> {16 System.out.println(" Lambda thread");17});output Lambda threadnewThread.join();
22 newThread.start();23 newThread.join();24} catch (InterruptedException e) {names ← [Charlie, Alice, Bob, David], numbers ← [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
29System.out.println("\nSorting:");3031List<String> names→ [Charlie, Alice, Bob, David] = new ArrayList<>(32 Arrays.asList("Charlie", "Alice", "Bob", "David"));3334names.sort((a, b) -> a.compareTo(b));35System.out.println(" By name: " + names[Alice, Bob, Charlie, David]);3637names.sort((a, b) -> Integer.compare(a.length(), b.length()));38System.out.println(" By length: " + names[Bob, Alice, David, Charlie]);3940names.sort((a, b) -> {41 char lastA = a.charAt(a.length() - 1);42 char lastB = b.charAt(b.length() - 1);43 return Character.compare(lastA, lastB);44});45System.out.println(" By last char: " + names[Bob, David, Alice, Charlie]);4647System.out.println("\nList processing:");4849List<Integer> numbers→ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] = new ArrayList<>(50 Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));5152System.out.print(" All: ");53numbers.forEach(n -> System.out.print(n + " "));54System.out.println();5556numbers.removeIf(n -> n % 2 == 0);57System.out.println(" After removing evens: " + numbers[1, 3, 5, 7, 9]);5859numbers.replaceAll(n -> n * 10);60System.out.println(" After * 10: " + numbers[10, 30, 50, 70, 90]);6162System.out.println("\nMap operations:");6364Map<String, Integer> scores→ {} = new LinkedHashMap<>();65scores.put("Alice", 85);66scores.put("Bob", 92);67scores.put("Charlie", 78);6869scores.forEach((name, score) -> 70 System.out.println(" " + name + ": " + score));7172scores.replaceAll((name, score) -> score + 5); // Curve grades73System.out.println(" After curve: " + scores{Alice=90, Bob=97, Charlie=83});7475scores.computeIfAbsent("David", k -> 80);76System.out.println(" After adding David: " + scores{Alice=90, Bob=97, Charlie=83, David=80});7778System.out.println("\nCustom callbacks:");7980processData(Arrays.asList(1, 2, 3, 4, 5),81 n -> n * 2,82 n -> System.out.println(" Processed: " + n)83);output Sorting: By name: [Alice, Bob, Charlie, David] By length: [Bob, Alice, David, Charlie] By last char: [Bob, David, Alice, Charlie] List processing: All: After removing evens: [1, 3, 5, 7, 9] After * 10: [10, 30, 50, 70, 90] Map operations: After curve: {Alice=90, Bob=97, Charlie=83} After adding David: {Alice=90, Bob=97, Charlie=83, David=80} Custom callbacks:static void processData(List<Integer> data, …
104static void processData(List<Integer> data[1, 2, 3, 4, 5],105 Function<Integer, Integer> processor⟨UseCases lambda A⟩,106 Consumer<Integer> outputter⟨UseCases lambda B⟩) {107 for (Integer item : data) {processed ← 2
pass 1 of 5106 Consumer<Integer> outputter) {107for (Integer item1 : data[1, 2, 3, 4, 5]) {108 Integer processed→ 2 = processor.apply(item1);109 outputter.accept(processed2);110}All 5 passes — pass 1 is the card above pass itemtextactiononClickprocessedthis.textbuttonthis.onClickvaluescutoff1 1 — — — 2 — — — — — 2 2 — — — 4 — — — — — 3 3 — — — 6 — — — — — 4 4 — — — 8 — — — — — 5 5 Click me ⟨UseCases lambda C⟩ ⟨UseCases lambda D⟩ 10 Click me ⟨Button E⟩ ⟨UseCases lambda C⟩ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 8 this.text ← Click me, button ← ⟨Button E⟩
87 Button button→ ⟨Button E⟩ = new Button("Click me");88 89 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 8;99 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String textClick me) {129 this.text→ Click me = textClick me;130 }this.onClick ← ⟨UseCases lambda C⟩
pass 1 of 289 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 8;99 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action⟨UseCases lambda C⟩) {133 this.onClick→ ⟨UseCases lambda C⟩ = action⟨UseCases lambda C⟩;134 }this.onClick ← ⟨UseCases lambda D⟩
pass 2 of 289 button.setOnClick(() -> System.out.println(" Button clicked!"));90 button.setOnClick(() -> System.out.println(" Action performed"));91 92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff = 8;99 filterAndPrint(values, n -> n > cutoff, "Greater than " + cutoff);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action⟨UseCases lambda D⟩) {133 this.onClick→ ⟨UseCases lambda D⟩ = action⟨UseCases lambda D⟩;134 }values ← [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], cutoff ← 8
92 button.click();93 94 System.out.println("\nConditional logic:");95 96 List<Integer> values→ [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);97 98 int cutoff→ 8 = 8;99 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n > cutoff, "Greater than " + cutoff8);100 filterAndPrint(values, n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102 }103 104 static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111 }112 113 static void filterAndPrint(List<Integer> list, 114 Predicate<Integer> filter,115 String label) {116 System.out.print(" " + label + ": ");117 list.stream()118 .filter(filter)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121 }122}123124class Button {125 private String text;126 private Runnable onClick;127 128 Button(String text) {129 this.text = text;130 }131 132 void setOnClick(Runnable action) {133 this.onClick = action;134 }135 136 void click() {137 if (onClick⟨UseCases lambda D⟩ != null) {138 onClick.run();139 }output Conditional logic:static void filterAndPrint(List<Integer> list, …
pass 1 of 398 int cutoff = 8;99 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n > cutoff, "Greater than " + cutoff8);100 filterAndPrint(values[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], n -> n % 2 == 0, "Even numbers");101 filterAndPrint(values, n -> n % 3 == 0, "Divisible by 3");102}103104static void processData(List<Integer> data,105 Function<Integer, Integer> processor,106 Consumer<Integer> outputter) {107 for (Integer item : data) {108 Integer processed = processor.apply(item);109 outputter.accept(processed);110 }111}112113static void filterAndPrint(List<Integer> list[1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 114 Predicate<Integer> filter⟨UseCases lambda F⟩,115 String labelGreater than 8) {116 System.out.print(" " + labelGreater than 8 + ": ");117 list.stream()118 .filter(filter⟨UseCases lambda F⟩)119 .forEach(n -> System.out.print(n + " "));120 System.out.println();121}output Greater than 8:All 3 passes — pass 1 is the card above pass filterlabelcutoff1 ⟨UseCases lambda F⟩ Greater than 8 8 2 ⟨UseCases lambda G⟩ Even numbers — 3 ⟨UseCases lambda H⟩ Divisible by 3 —
Collections, streams, event handlers, callbacks - anywhere functional interfaces are used.
Exercise: Practical.java
Refactor anonymous classes to lambdas