Control Flow
Break and Continue
Loop Control
You're scanning a list of 10,000 products for item #4521. Once found, why keep
searching? break lets you exit immediately. Or you're processing orders but
want to skip cancelled ones - continue jumps to the next iteration.
Find first match (break)
Stop searching once you find what you're looking for.
Break.java
public class Break {
public static void main(String[] args) {
int[] numbers = {10, 25, 30, 42, 55, 60};
int target = ;
int foundIndex = -1;
for (int i = 0; i < numbers.length; i++) {
System.out.println("Checking index " + i + ": " + numbers[i]);
if (numbers[i] == target) {
foundIndex = i;
break;
}
}
if (foundIndex != -1) {
System.out.println("Found " + target + " at index " + foundIndex);
} else {
System.out.println(target + " not found");
}
// Without break, would check all elements unnecessarily
// With break, stops at first match
}
}
public class Break {
public static void main(String[] args) {
int[] numbers = {10, 25, 30, 42, 55, 60};
int target = ;
int foundIndex = -1;
for (int i = 0; i < numbers.length; i++) {
System.out.println("Checking index " + i + ": " + numbers[i]);
if (numbers[i] == target) {
foundIndex = i;
break;
}
}
if (foundIndex != -1) {
System.out.println("Found " + target + " at index " + foundIndex);
} else {
System.out.println(target + " not found");
}
// Without break, would check all elements unnecessarily
// With break, stops at first match
}
}
public class Break {
public static void main(String[] args) {
int[] numbers = {10, 25, 30, 42, 55, 60};
int target = ;
int foundIndex = -1;
for (int i = 0; i < numbers.length; i++) {
System.out.println("Checking index " + i + ": " + numbers[i]);
if (numbers[i] == target) {
foundIndex = i;
break;
}
}
if (foundIndex != -1) {
System.out.println("Found " + target + " at index " + foundIndex);
} else {
System.out.println(target + " not found");
}
// Without break, would check all elements unnecessarily
// With break, stops at first match
}
}
break exits the innermost loop immediately. More efficient than checking all.
break
Exit the innermost loop immediately. Loop terminates.
Skip invalid entries (continue)
Skip items that don't meet criteria without stopping the loop.
Continue.java
public class Continue {
public static void main(String[] args) {
int[] scores = {85, -1, 92, 0, 78, -5, 95}; // -1 and -5 are invalid
int sum = 0;
int count = 0;
System.out.println("Processing scores:");
for (int score : scores) {
if (score < 0) {
System.out.println(" Skipping invalid: " + score);
continue;
}
System.out.println(" Adding: " + score);
sum += score;
count++;
}
System.out.println("Valid scores: " + count);
System.out.println("Sum: " + sum);
if (count > 0) {
System.out.println("Average: " + (sum / count));
}
}
}
continue jumps to the next iteration, skipping the rest of the loop body.
continue
Skip rest of current iteration, go to next iteration.
Early exit on error
Stop processing if something goes wrong.
EarlyExit.java
public class EarlyExit {
public static void main(String[] args) {
String[] commands = ;
boolean success = true;
for (String cmd : commands) {
System.out.println("Executing: " + cmd);
// Stop on error
if (cmd.equals("error")) {
System.out.println("ERROR: Operation failed!");
success = false;
break;
}
System.out.println(" Done.");
}
if (success) {
System.out.println("All commands completed successfully.");
} else {
System.out.println("Processing stopped due to error.");
}
}
}
public class EarlyExit {
public static void main(String[] args) {
String[] commands = ;
boolean success = true;
for (String cmd : commands) {
System.out.println("Executing: " + cmd);
// Stop on error
if (cmd.equals("error")) {
System.out.println("ERROR: Operation failed!");
success = false;
break;
}
System.out.println(" Done.");
}
if (success) {
System.out.println("All commands completed successfully.");
} else {
System.out.println("Processing stopped due to error.");
}
}
}
public class EarlyExit {
public static void main(String[] args) {
String[] commands = ;
boolean success = true;
for (String cmd : commands) {
System.out.println("Executing: " + cmd);
// Stop on error
if (cmd.equals("error")) {
System.out.println("ERROR: Operation failed!");
success = false;
break;
}
System.out.println(" Done.");
}
if (success) {
System.out.println("All commands completed successfully.");
} else {
System.out.println("Processing stopped due to error.");
}
}
}
Validate early and break if invalid - cleaner than deep nesting.
Process until sentinel
Process data until you encounter a special "stop" value.
Sentinel.java
public class Sentinel {
public static void main(String[] args) {
// Data with sentinel value -1 marking end
int[] data = ;
System.out.println("Processing until sentinel (-1):");
int sum = 0;
for (int value : data) {
if (value == -1) {
System.out.println("Sentinel found, stopping.");
break;
}
System.out.println("Processing: " + value);
sum += value;
}
System.out.println("Sum of processed values: " + sum);
// Alternative: while loop
System.out.println("\nUsing while loop:");
int i = 0;
int sum2 = 0;
while (i < data.length && data[i] != -1) {
sum2 += data[i];
i++;
}
System.out.println("Sum: " + sum2);
}
}
public class Sentinel {
public static void main(String[] args) {
// Data with sentinel value -1 marking end
int[] data = ;
System.out.println("Processing until sentinel (-1):");
int sum = 0;
for (int value : data) {
if (value == -1) {
System.out.println("Sentinel found, stopping.");
break;
}
System.out.println("Processing: " + value);
sum += value;
}
System.out.println("Sum of processed values: " + sum);
// Alternative: while loop
System.out.println("\nUsing while loop:");
int i = 0;
int sum2 = 0;
while (i < data.length && data[i] != -1) {
sum2 += data[i];
i++;
}
System.out.println("Sum: " + sum2);
}
}
public class Sentinel {
public static void main(String[] args) {
// Data with sentinel value -1 marking end
int[] data = ;
System.out.println("Processing until sentinel (-1):");
int sum = 0;
for (int value : data) {
if (value == -1) {
System.out.println("Sentinel found, stopping.");
break;
}
System.out.println("Processing: " + value);
sum += value;
}
System.out.println("Sum of processed values: " + sum);
// Alternative: while loop
System.out.println("\nUsing while loop:");
int i = 0;
int sum2 = 0;
while (i < data.length && data[i] != -1) {
sum2 += data[i];
i++;
}
System.out.println("Sum: " + sum2);
}
}
Sentinel values signal "end of data" - common in file and stream processing.
sentinel
Special value marking end of data: -1, null, "END", etc.
Labeled break (nested loops)
Break out of outer loops using labels (Java-specific).
LabeledBreak.java
public class LabeledBreak {
public static void main(String[] args) {
int[][] grid = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int target = ;
int foundRow = -1;
int foundCol = -1;
// Without label: only breaks inner loop
System.out.println("Search without label (broken):");
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break; // Only breaks inner loop!
}
}
System.out.println("Still in outer loop, row " + row);
}
// With label: breaks outer loop
System.out.println("\nSearch with label (correct):");
foundRow = -1;
foundCol = -1;
search:
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break search; // Breaks outer loop!
}
}
}
if (foundRow != -1) {
System.out.println("Found " + target + " at [" + foundRow + "][" + foundCol + "]");
} else {
System.out.println(target + " not found");
}
}
}
public class LabeledBreak {
public static void main(String[] args) {
int[][] grid = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int target = ;
int foundRow = -1;
int foundCol = -1;
// Without label: only breaks inner loop
System.out.println("Search without label (broken):");
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break; // Only breaks inner loop!
}
}
System.out.println("Still in outer loop, row " + row);
}
// With label: breaks outer loop
System.out.println("\nSearch with label (correct):");
foundRow = -1;
foundCol = -1;
search:
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break search; // Breaks outer loop!
}
}
}
if (foundRow != -1) {
System.out.println("Found " + target + " at [" + foundRow + "][" + foundCol + "]");
} else {
System.out.println(target + " not found");
}
}
}
public class LabeledBreak {
public static void main(String[] args) {
int[][] grid = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int target = ;
int foundRow = -1;
int foundCol = -1;
// Without label: only breaks inner loop
System.out.println("Search without label (broken):");
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break; // Only breaks inner loop!
}
}
System.out.println("Still in outer loop, row " + row);
}
// With label: breaks outer loop
System.out.println("\nSearch with label (correct):");
foundRow = -1;
foundCol = -1;
search:
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break search; // Breaks outer loop!
}
}
}
if (foundRow != -1) {
System.out.println("Found " + target + " at [" + foundRow + "][" + foundCol + "]");
} else {
System.out.println(target + " not found");
}
}
}
public class LabeledBreak {
public static void main(String[] args) {
int[][] grid = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int target = ;
int foundRow = -1;
int foundCol = -1;
// Without label: only breaks inner loop
System.out.println("Search without label (broken):");
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break; // Only breaks inner loop!
}
}
System.out.println("Still in outer loop, row " + row);
}
// With label: breaks outer loop
System.out.println("\nSearch with label (correct):");
foundRow = -1;
foundCol = -1;
search:
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
if (grid[row][col] == target) {
foundRow = row;
foundCol = col;
break search; // Breaks outer loop!
}
}
}
if (foundRow != -1) {
System.out.println("Found " + target + " at [" + foundRow + "][" + foundCol + "]");
} else {
System.out.println(target + " not found");
}
}
}
Labels let you break from nested loops - useful for searching 2D structures.
@concept labeled break
Java: outer: for(...) { ... break outer; } - break outer loop.
Exercise: Refactoring.java
Explore refactoring techniques to reduce break/continue for cleaner code