ArrayList - Java Programming

Your shopping cart can't be a fixed-size array - users add and remove items constantly. ArrayList grows and shrinks automatically, handling the resizing so you can focus on your logic.

Add items to a cart

Create an ArrayList and add elements dynamically.

                            ShoppingCart.java
                        
Replay: real traced execution (multi-file project)

                            import java.util.ArrayList;

public class ShoppingCart {
    public static void main(String[] args) {
        // Create an empty shopping cart
        ArrayList<String> cart = new ArrayList<>();

        System.out.println("=== Shopping Session ===");
        System.out.println("Cart starts empty: " + cart);
        System.out.println("Items in cart: " + cart.size());

        // Add items to cart
        cart.add("Milk");
        System.out.println("Added Milk: " + cart);

        cart.add("Bread");
        System.out.println("Added Bread: " + cart);

        cart.add("Eggs");
        System.out.println("Added Eggs: " + cart);

        // Add more items
        cart.add("Butter");
        cart.add("Cheese");
        cart.add("Yogurt");
        System.out.println("Added more: " + cart);

        // Insert at specific position (beginning)
        cart.add(0, "Coffee");
        System.out.println("Inserted Coffee at start: " + cart);

        System.out.println("\n=== Final Cart ===");
        System.out.println("Items: " + cart);
        System.out.println("Total items: " + cart.size());
    }
}

                        
1cart ← []⋯4public class ShoppingCart {5    public static void main(String[] args) {6        // Create an empty shopping cart  //#?create7        ArrayList<String> cart→ [] = new ArrayList<>();8        9        System.out.println("=== Shopping Session ===");10        System.out.println("Cart starts empty: " + cart[]);11        System.out.println("Items in cart: " + cart.size());12        13        // Add items to cart14        cart.add("Milk");     //?add15        System.out.println("Added Milk: " + cart[Milk]);16        17        cart.add("Bread");18        System.out.println("Added Bread: " + cart[Milk, Bread]);19        20        cart.add("Eggs");21        System.out.println("Added Eggs: " + cart[Milk, Bread, Eggs]);22        23        // Add more items24        cart.add("Butter");   //@var=_,!25        cart.add("Cheese");   //@var=_,!26        cart.add("Yogurt");   //@var=_,!27        System.out.println("Added more: " + cart[Milk, Bread, Eggs, Butter, Cheese, Yogurt]);  //@var=_,!28        29        // Insert at specific position (beginning)30        cart.add(0, "Coffee");  //?insert31        System.out.println("Inserted Coffee at start: " + cart[Coffee, Milk, Bread, Eggs, Butter, Cheese, Yogurt]);32        33        System.out.println("\n=== Final Cart ===");34        System.out.println("Items: " + cart[Coffee, Milk, Bread, Eggs, Butter, Cheese, Yogurt]);35        System.out.println("Total items: " + cart.size());36    }⋯output=== Shopping Session ===
Cart starts empty: []
Items in cart: 0
Added Milk: [Milk]
Added Bread: [Milk, Bread]
Added Eggs: [Milk, Bread, Eggs]
Added more: [Milk, Bread, Eggs, Butter, Cheese, Yogurt]
Inserted Coffee at start: [Coffee, Milk, Bread, Eggs, Butter, Cheese, Yogurt]

=== Final Cart ===
Items: [Coffee, Milk, Bread, Eggs, Butter, Cheese, Yogurt]
Total items: 7

ArrayList<String> holds strings. Use add() to append items.

ArrayList Resizable array: grows automatically. Use `ArrayList<Type>` with wrapper types.

Access items by position

Get an item at a specific index.

                            index
                            index = 2 (default)index = 10
                        

                            GetItem.java
                        
Replay: real traced execution (multi-file project)

                            import java.util.ArrayList;
import java.util.Arrays;

public class GetItem {
    public static void main(String[] args) {
        // Initialize cart with items
        ArrayList<String> cart = new ArrayList<>(
            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")
        );

        System.out.println("=== Shopping Cart ===");
        System.out.println("Cart: " + cart);
        System.out.println("Total items: " + cart.size());

        // Access items by index
        int index = 2;

        System.out.println("\n=== Access by Index ===");
        System.out.println("First item (index 0): " + cart.get(0));
        System.out.println("Last item (index " + (cart.size()-1) + "): " +
            cart.get(cart.size() - 1));

        // Safe access with bounds check
        if (index >= 0 && index < cart.size()) {
            System.out.println("Item at index " + index + ": " + cart.get(index));
        } else {
            System.out.println("Index " + index + " is out of bounds!");
            System.out.println("Valid indices: 0 to " + (cart.size() - 1));
        }

        // Display all with indices
        System.out.println("\n=== Cart with Indices ===");
        for (int i = 0; i < cart.size(); i++) {
            System.out.println("[" + i + "] " + cart.get(i));
        }
    }
}
import java.util.ArrayList;
import java.util.Arrays;

public class GetItem {
    public static void main(String[] args) {
        // Initialize cart with items
        ArrayList<String> cart = new ArrayList<>(
            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")
        );

        System.out.println("=== Shopping Cart ===");
        System.out.println("Cart: " + cart);
        System.out.println("Total items: " + cart.size());

        // Access items by index
        int index = 10;

        System.out.println("\n=== Access by Index ===");
        System.out.println("First item (index 0): " + cart.get(0));
        System.out.println("Last item (index " + (cart.size()-1) + "): " +
            cart.get(cart.size() - 1));

        // Safe access with bounds check
        if (index >= 0 && index < cart.size()) {
            System.out.println("Item at index " + index + ": " + cart.get(index));
        } else {
            System.out.println("Index " + index + " is out of bounds!");
            System.out.println("Valid indices: 0 to " + (cart.size() - 1));
        }

        // Display all with indices
        System.out.println("\n=== Cart with Indices ===");
        for (int i = 0; i < cart.size(); i++) {
            System.out.println("[" + i + "] " + cart.get(i));
        }
    }
}

                        
1cart ← [Coffee, Milk, Bread, Eggs, Butter], index ← 2⋯5public class GetItem {6    public static void main(String[] args) {7        // Initialize cart with items8        ArrayList<String> cart→ [Coffee, Milk, Bread, Eggs, Butter] = new ArrayList<>(9            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")10        );11        12        System.out.println("=== Shopping Cart ===");13        System.out.println("Cart: " + cart[Coffee, Milk, Bread, Eggs, Butter]);14        System.out.println("Total items: " + cart.size());15        16        // Access items by index  //#?get17        int index→ 2 = 2;  //@var=_,1018        19        System.out.println("\n=== Access by Index ===");20        System.out.println("First item (index 0): " + cart.get(0));21        System.out.println("Last item (index " + (cart.size()-1) + "): " + 22            cart.get(cart.size() - 1));⋯output=== Shopping Cart ===
Cart: [Coffee, Milk, Bread, Eggs, Butter]
Total items: 5

=== Access by Index ===
First item (index 0): Coffee
Last item (index 4): Butter
2if (index >= 0 && index < cart.size())⋯24// Safe access with bounds check25if (index2 >= 0 && index < cart.size()) {  //?bounds26    System.out.println("Item at index " + index2 + ": " + cart.get(index));27} else {⋯outputItem at index 2: Bread
3System.out.println(" === Cart with Indices ===");⋯32// Display all with indices33System.out.println("\n=== Cart with Indices ===");34for (int i = 0; i < cart.size(); i++) {⋯output
=== Cart with Indices ===
4for (int i = 0; i < cart.size(); i++)pass 1 of 5⋯33System.out.println("\n=== Cart with Indices ===");34for (int i0 = 0; i < cart.size(); i++) {35    System.out.println("[" + i0 + "] " + cart.get(i));36}⋯output[0] CoffeeAll 5 passes — pass 1 is the card abovepassi
10
21
32
43
54
1cart ← [Coffee, Milk, Bread, Eggs, Butter], index ← 10⋯4public class GetItem {5    public static void main(String[] args) {6        // Initialize cart with items7        ArrayList<String> cart→ [Coffee, Milk, Bread, Eggs, Butter] = new ArrayList<>(8            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")9        );10        11        System.out.println("=== Shopping Cart ===");12        System.out.println("Cart: " + cart[Coffee, Milk, Bread, Eggs, Butter]);13        System.out.println("Total items: " + cart.size());14        15        // Access items by index16        int index→ 10 = 10;17        18        System.out.println("\n=== Access by Index ===");19        System.out.println("First item (index 0): " + cart.get(0));20        System.out.println("Last item (index " + (cart.size()-1) + "): " + 21            cart.get(cart.size() - 1));⋯output=== Shopping Cart ===
Cart: [Coffee, Milk, Bread, Eggs, Butter]
Total items: 5

=== Access by Index ===
First item (index 0): Coffee
Last item (index 4): Butter
2else⋯25    System.out.println("Item at index " + index + ": " + cart.get(index));26} else {27    System.out.println("Index " + index10 + " is out of bounds!");28    System.out.println("Valid indices: 0 to " + (cart.size() - 1));29}⋯outputIndex 10 is out of bounds!
Valid indices: 0 to 4
3System.out.println(" === Cart with Indices ===");⋯31// Display all with indices32System.out.println("\n=== Cart with Indices ===");33for (int i = 0; i < cart.size(); i++) {⋯output
=== Cart with Indices ===
4for (int i = 0; i < cart.size(); i++)pass 1 of 5⋯32System.out.println("\n=== Cart with Indices ===");33for (int i0 = 0; i < cart.size(); i++) {34    System.out.println("[" + i0 + "] " + cart.get(i));35}⋯output[0] CoffeeAll 5 passes — pass 1 is the card abovepassi
10
21
32
43
54

All 5 passes — pass 1 is the card above
pass	`i`
1	0
2	1
3	2
4	3
5	4

All 5 passes — pass 1 is the card above
pass	`i`
1	0
2	1
3	2
4	3
5	4

Use get(index) to retrieve items. Index starts at 0.

Remove items from cart

Remove items by value or by index.

                            RemoveItem.java
                        
Replay: real traced execution (multi-file project)

                            import java.util.ArrayList;
import java.util.Arrays;

public class RemoveItem {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>(
            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Milk", "Butter")
        );

        System.out.println("=== Initial Cart ===");
        System.out.println(cart);

        // Remove by value (removes first occurrence)
        String toRemove = "Milk";
        boolean removed = cart.remove(toRemove);
        System.out.println("\nRemove \"" + toRemove + "\": " + removed);
        System.out.println("Cart: " + cart);
        System.out.println("Note: Second 'Milk' still there!");

        // Remove by index
        int removeIndex = 1;
        String removedItem = cart.remove(removeIndex);
        System.out.println("\nRemoved at index " + removeIndex + ": " + removedItem);
        System.out.println("Cart: " + cart);

        // Try to remove non-existent item
        String notInCart = "Pizza";
        boolean result = cart.remove(notInCart);
        System.out.println("\nRemove \"" + notInCart + "\": " + result);

        // Remove all remaining items
        System.out.println("\n=== Clearing Cart ===");
        System.out.println("Before clear: " + cart.size() + " items");
        cart.clear();
        System.out.println("After clear: " + cart.size() + " items");
        System.out.println("Cart is empty: " + cart.isEmpty());
    }
}

                        
1cart ← [Coffee, Milk, Bread, Eggs, Milk, Butter], toRemove ← Milk⋯5public class RemoveItem {6    public static void main(String[] args) {7        ArrayList<String> cart→ [Coffee, Milk, Bread, Eggs, Milk, Butter] = new ArrayList<>(8            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Milk", "Butter")9        );10        11        System.out.println("=== Initial Cart ===");12        System.out.println(cart[Coffee, Milk, Bread, Eggs, Milk, Butter]);13        14        // Remove by value (removes first occurrence)  //#?removeVal15        String toRemove→ Milk = "Milk";  //@var=_,!16        boolean removed→ true = cart.remove(toRemoveMilk);17        System.out.println("\nRemove \"" + toRemoveMilk + "\": " + removedtrue);18        System.out.println("Cart: " + cart[Coffee, Bread, Eggs, Milk, Butter]);19        System.out.println("Note: Second 'Milk' still there!");20        21        // Remove by index  //#?removeIdx22        int removeIndex→ 1 = 1;  //@var=!,_23        String removedItem→ Bread = cart.remove(removeIndex1);  //@var=!,_24        System.out.println("\nRemoved at index " + removeIndex1 + ": " + removedItemBread);  //@var=!,_25        System.out.println("Cart: " + cart[Coffee, Eggs, Milk, Butter]);  //@var=!,_26        27        // Try to remove non-existent item28        String notInCart→ Pizza = "Pizza";29        boolean result→ false = cart.remove(notInCartPizza);30        System.out.println("\nRemove \"" + notInCartPizza + "\": " + resultfalse);31        32        // Remove all remaining items33        System.out.println("\n=== Clearing Cart ===");34        System.out.println("Before clear: " + cart.size() + " items");35        cart.clear();  //?clear36        System.out.println("After clear: " + cart.size() + " items");37        System.out.println("Cart is empty: " + cart.isEmpty());38    }⋯output=== Initial Cart ===
[Coffee, Milk, Bread, Eggs, Milk, Butter]

Remove "Milk": true
Cart: [Coffee, Bread, Eggs, Milk, Butter]
Note: Second 'Milk' still there!

Removed at index 1: Bread
Cart: [Coffee, Eggs, Milk, Butter]

Remove "Pizza": false

=== Clearing Cart ===
Before clear: 4 items
After clear: 0 items
Cart is empty: true

remove("item") by value, remove(0) by index. Returns the removed element.

Check if item exists

Test whether an item is in the list.

                            searchItem
                            searchItem = "Milk" (default)searchItem = "Pizza"
                        

                            ContainsCheck.java
                        
Replay: real traced execution (multi-file project)

                            import java.util.ArrayList;
import java.util.Arrays;

public class ContainsCheck {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>(
            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")
        );

        System.out.println("=== Shopping Cart ===");
        System.out.println(cart);

        // Check if item exists
        String searchItem = "Milk";

        System.out.println("\n=== Membership Check ===");
        if (cart.contains(searchItem)) {
            System.out.println("✓ \"" + searchItem + "\" is in the cart");

            // Find its position
            int position = cart.indexOf(searchItem);
            System.out.println("  Position: index " + position);
        } else {
            System.out.println("✗ \"" + searchItem + "\" is NOT in the cart");
            System.out.println("  Would you like to add it?");
        }

        // Check multiple items
        System.out.println("\n=== Shopping List Check ===");
        String[] shoppingList = {"Milk", "Eggs", "Cheese", "Bread", "Yogurt"};

        ArrayList<String> needToBuy = new ArrayList<>();
        ArrayList<String> alreadyHave = new ArrayList<>();

        for (String item : shoppingList) {
            if (cart.contains(item)) {
                alreadyHave.add(item);
            } else {
                needToBuy.add(item);
            }
        }

        System.out.println("Already in cart: " + alreadyHave);
        System.out.println("Still need to buy: " + needToBuy);
    }
}
import java.util.ArrayList;
import java.util.Arrays;

public class ContainsCheck {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>(
            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")
        );

        System.out.println("=== Shopping Cart ===");
        System.out.println(cart);

        // Check if item exists
        String searchItem = "Pizza";

        System.out.println("\n=== Membership Check ===");
        if (cart.contains(searchItem)) {
            System.out.println("✓ \"" + searchItem + "\" is in the cart");

            // Find its position
            int position = cart.indexOf(searchItem);
            System.out.println("  Position: index " + position);
        } else {
            System.out.println("✗ \"" + searchItem + "\" is NOT in the cart");
            System.out.println("  Would you like to add it?");
        }

        // Check multiple items
        System.out.println("\n=== Shopping List Check ===");
        String[] shoppingList = {"Milk", "Eggs", "Cheese", "Bread", "Yogurt"};

        ArrayList<String> needToBuy = new ArrayList<>();
        ArrayList<String> alreadyHave = new ArrayList<>();

        for (String item : shoppingList) {
            if (cart.contains(item)) {
                alreadyHave.add(item);
            } else {
                needToBuy.add(item);
            }
        }

        System.out.println("Already in cart: " + alreadyHave);
        System.out.println("Still need to buy: " + needToBuy);
    }
}

                        
1cart ← [Coffee, Milk, Bread, Eggs, Butter], searchItem ← Milk⋯5public class ContainsCheck {6    public static void main(String[] args) {7        ArrayList<String> cart→ [Coffee, Milk, Bread, Eggs, Butter] = new ArrayList<>(8            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")9        );10        11        System.out.println("=== Shopping Cart ===");12        System.out.println(cart[Coffee, Milk, Bread, Eggs, Butter]);13        14        // Check if item exists  //#?contains15        String searchItem→ Milk = "Milk";  //@var=_,Pizza16        17        System.out.println("\n=== Membership Check ===");18        if (cart.contains(searchItem)) {⋯output=== Shopping Cart ===
[Coffee, Milk, Bread, Eggs, Butter]

=== Membership Check ===
2position ← 1⋯17System.out.println("\n=== Membership Check ===");18if (cart.contains(searchItemMilk)) {19    System.out.println("✓ \"" + searchItemMilk + "\" is in the cart");20    21    // Find its position22    int position→ 1 = cart.indexOf(searchItemMilk);  //?index23    System.out.println("  Position: index " + position1);24} else {⋯output✓ "Milk" is in the cart
  Position: index 1
3needToBuy ← [], alreadyHave ← []⋯29// Check multiple items30System.out.println("\n=== Shopping List Check ===");31String[] shoppingList = {"Milk", "Eggs", "Cheese", "Bread", "Yogurt"};3233ArrayList<String> needToBuy→ [] = new ArrayList<>();34ArrayList<String> alreadyHave→ [] = new ArrayList<>();⋯output
=== Shopping List Check ===
4for (String item : shoppingList)pass 1 of 5⋯36for (String itemMilk : shoppingList) {37    if (cart.contains(item)) {⋯All 5 passes — pass 1 is the card abovepassitem
1Milk
2Eggs
3Cheese
4Bread
5Yogurt
5if (cart.contains(item))pass 1 of 3⋯36for (String item : shoppingList) {37    if (cart.contains(itemMilk)) {38        alreadyHave.add(itemMilk);39    } else {⋯All 3 passes — pass 1 is the card abovepassitem
1Milk
2Eggs
3Bread
6elsepass 1 of 2⋯38    alreadyHave.add(item);39} else {40    needToBuy.add(itemCheese);41}⋯
7elsepass 2 of 2⋯38    alreadyHave.add(item);39} else {40    needToBuy.add(itemYogurt);41}⋯
8System.out.println("Already in cart: " + alreadyHave);⋯44    System.out.println("Already in cart: " + alreadyHave[Milk, Eggs, Bread]);45    System.out.println("Still need to buy: " + needToBuy[Cheese, Yogurt]);46}⋯outputAlready in cart: [Milk, Eggs, Bread]
Still need to buy: [Cheese, Yogurt]
1cart ← [Coffee, Milk, Bread, Eggs, Butter], searchItem ← Pizza⋯4public class ContainsCheck {5    public static void main(String[] args) {6        ArrayList<String> cart→ [Coffee, Milk, Bread, Eggs, Butter] = new ArrayList<>(7            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")8        );9        10        System.out.println("=== Shopping Cart ===");11        System.out.println(cart[Coffee, Milk, Bread, Eggs, Butter]);12        13        // Check if item exists14        String searchItem→ Pizza = "Pizza";15        16        System.out.println("\n=== Membership Check ===");17        if (cart.contains(searchItem)) {⋯output=== Shopping Cart ===
[Coffee, Milk, Bread, Eggs, Butter]

=== Membership Check ===
2else⋯22    System.out.println("  Position: index " + position);23} else {24    System.out.println("✗ \"" + searchItemPizza + "\" is NOT in the cart");25    System.out.println("  Would you like to add it?");26}⋯output✗ "Pizza" is NOT in the cart
  Would you like to add it?
3needToBuy ← [], alreadyHave ← []⋯28// Check multiple items29System.out.println("\n=== Shopping List Check ===");30String[] shoppingList = {"Milk", "Eggs", "Cheese", "Bread", "Yogurt"};3132ArrayList<String> needToBuy→ [] = new ArrayList<>();33ArrayList<String> alreadyHave→ [] = new ArrayList<>();⋯output
=== Shopping List Check ===
4for (String item : shoppingList)pass 1 of 5⋯35for (String itemMilk : shoppingList) {36    if (cart.contains(item)) {⋯All 5 passes — pass 1 is the card abovepassitem
1Milk
2Eggs
3Cheese
4Bread
5Yogurt
5if (cart.contains(item))pass 1 of 3⋯35for (String item : shoppingList) {36    if (cart.contains(itemMilk)) {37        alreadyHave.add(itemMilk);38    } else {⋯All 3 passes — pass 1 is the card abovepassitem
1Milk
2Eggs
3Bread
6elsepass 1 of 2⋯37    alreadyHave.add(item);38} else {39    needToBuy.add(itemCheese);40}⋯
7elsepass 2 of 2⋯37    alreadyHave.add(item);38} else {39    needToBuy.add(itemYogurt);40}⋯
8System.out.println("Already in cart: " + alreadyHave);⋯43    System.out.println("Already in cart: " + alreadyHave[Milk, Eggs, Bread]);44    System.out.println("Still need to buy: " + needToBuy[Cheese, Yogurt]);45}⋯outputAlready in cart: [Milk, Eggs, Bread]
Still need to buy: [Cheese, Yogurt]

All 5 passes — pass 1 is the card above
pass	`item`
1	Milk
2	Eggs
3	Cheese
4	Bread
5	Yogurt

All 3 passes — pass 1 is the card above
pass	`item`
1	Milk
2	Eggs
3	Bread

All 5 passes — pass 1 is the card above
pass	`item`
1	Milk
2	Eggs
3	Cheese
4	Bread
5	Yogurt

All 3 passes — pass 1 is the card above
pass	`item`
1	Milk
2	Eggs
3	Bread

contains() returns boolean. Useful before processing.

contains Membership test: `list.contains("item")`. Returns true/false.

Loop through all items

Iterate over all elements in the ArrayList.

                            IterateAll.java
                        
Replay: real traced execution (multi-file project)

                            import java.util.ArrayList;
import java.util.Arrays;

public class IterateAll {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>(
            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")
        );
        double[] prices = {4.99, 3.49, 2.99, 5.99, 4.49};

        System.out.println("=== Shopping Cart ===\n");

        // Method 1: Enhanced for-each (most common)
        System.out.println("1. For-each loop:");
        for (String item : cart) {
            System.out.println("   • " + item);
        }

        // Method 2: Index-based (when you need position)
        System.out.println("\n2. Index-based loop (with prices):");
        double total = 0;
        for (int i = 0; i < cart.size(); i++) {
            System.out.printf("   %d. %-10s $%.2f%n", i+1, cart.get(i), prices[i]);
            total += prices[i];
        }
        System.out.printf("   Total: $%.2f%n", total);

        // Method 3: forEach with lambda (Java 8+)
        System.out.println("\n3. forEach with lambda:");
        cart.forEach(item -> System.out.println("   → " + item));

        // Method 4: forEach with method reference
        System.out.println("\n4. Method reference:");
        cart.forEach(System.out::println);

        // Bonus: Iterate with index using forEach
        System.out.println("\n5. Indexed forEach (manual counter):");
        int[] counter = {0};  // Array trick for lambda
        cart.forEach(item -> {
            System.out.println("   [" + counter[0] + "] " + item);
            counter[0]++;
        });
    }
}

                        
1cart ← [Coffee, Milk, Bread, Eggs, Butter]⋯4public class IterateAll {5    public static void main(String[] args) {6        ArrayList<String> cart→ [Coffee, Milk, Bread, Eggs, Butter] = new ArrayList<>(7            Arrays.asList("Coffee", "Milk", "Bread", "Eggs", "Butter")8        );9        double[] prices = {4.99, 3.49, 2.99, 5.99, 4.49};10        11        System.out.println("=== Shopping Cart ===\n");12        13        // Method 1: Enhanced for-each (most common)  //#?foreach14        System.out.println("1. For-each loop:");15        for (String item : cart) {⋯output=== Shopping Cart ===
1. For-each loop:
2for (String item : cart)pass 1 of 5⋯14System.out.println("1. For-each loop:");15for (String itemCoffee : cart[Coffee, Milk, Bread, Eggs, Butter]) {16    System.out.println("   • " + itemCoffee);17}⋯output   • CoffeeAll 5 passes — pass 1 is the card abovepassitem
1Coffee
2Milk
3Bread
4Eggs
5Butter
3total ← 0.0⋯19// Method 2: Index-based (when you need position)  //#?indexed20System.out.println("\n2. Index-based loop (with prices):");21double total→ 0.0 = 0;22for (int i = 0; i < cart.size(); i++) {⋯output
2. Index-based loop (with prices):
4total ← 4.99pass 1 of 5⋯21double total = 0;22for (int i0 = 0; i < cart.size(); i++) {23    System.out.printf("   %d. %-10s $%.2f%n", i0+1, cart.get(i), prices[i]4.99);24    total→ 4.99 += prices[i]4.99;25}⋯All 5 passes — pass 1 is the card abovepassiprices[i]total
104.990.0 → 4.99
213.494.99 → 8.48
322.998.48 → 11.47
435.9911.47 → 17.46
544.4917.46 → 21.950000000000003
5System.out.printf("   Total: $%.2f%n", total);⋯25    }26    System.out.printf("   Total: $%.2f%n", total21.950000000000003);27    28    // Method 3: forEach with lambda (Java 8+)  //#?lambda29    System.out.println("\n3. forEach with lambda:");30    cart.forEach(item -> System.out.println("   → " + item));31    32    // Method 4: forEach with method reference33    System.out.println("\n4. Method reference:");34    cart.forEach(System.out::println);35    36    // Bonus: Iterate with index using forEach37    System.out.println("\n5. Indexed forEach (manual counter):");38    int[] counter = {0};  // Array trick for lambda39    cart.forEach(item -> {40        System.out.println("   [" + counter[0] + "] " + item);41        counter[0]++;42    });43}⋯output
3. forEach with lambda:

4. Method reference:

5. Indexed forEach (manual counter):
6item ->pass 1 of 5⋯38int[] counter = {0};  // Array trick for lambda39cart.forEach(item -> {40    System.out.println("   [" + counter[0] + "] " + item);41    counter[0]++;42});⋯output   [0] Coffee

All 5 passes — pass 1 is the card above
pass	`item`
1	Coffee
2	Milk
3	Bread
4	Eggs
5	Butter

All 5 passes — pass 1 is the card above
pass	`i`	`prices[i]`	`total`
1	0	4.99	0.0 → 4.99
2	1	3.49	4.99 → 8.48
3	2	2.99	8.48 → 11.47
4	3	5.99	11.47 → 17.46
5	4	4.49	17.46 → 21.950000000000003

Use for-each: for (String item : cart). Cleaner than index-based loops.

Exercise: ArraylistIntegers.java

Work with ArrayList<Integer> and wrapper classes