Java Loops

for Loop

Use a for loop when you know exactly how many times to iterate. It has three parts: initialization, condition, and update.

for, while, do-while

public class Loops {
    public static void main(String[] args) {

        // for loop
        System.out.println("--- for loop ---");
        for (int i = 1; i <= 5; i++) {
            System.out.print(i + " ");  // 1 2 3 4 5
        }
        System.out.println();

        // while loop — condition checked before each iteration
        System.out.println("--- while loop ---");
        int n = 1;
        while (n <= 5) {
            System.out.print(n + " ");
            n++;
        }
        System.out.println();

        // do-while loop — body executes at least once
        System.out.println("--- do-while loop ---");
        int x = 1;
        do {
            System.out.print(x + " ");
            x++;
        } while (x <= 5);
        System.out.println();
    }
}

for-each Loop (Enhanced for)

The enhanced for loop iterates over arrays and collections without needing an index variable. It's cleaner and less error-prone.

for-each, break & continue

public class ForEach {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50};

        // for-each loop
        System.out.println("--- for-each ---");
        for (int num : numbers) {
            System.out.print(num + " ");  // 10 20 30 40 50
        }
        System.out.println();

        // break — exits the loop immediately
        System.out.println("--- break ---");
        for (int i = 1; i <= 10; i++) {
            if (i == 6) break;
            System.out.print(i + " ");  // 1 2 3 4 5
        }
        System.out.println();

        // continue — skips the current iteration
        System.out.println("--- continue (skip evens) ---");
        for (int i = 1; i <= 10; i++) {
            if (i % 2 == 0) continue;
            System.out.print(i + " ");  // 1 3 5 7 9
        }
        System.out.println();
    }
}

Nested Loops

A loop inside another loop is called a nested loop. Commonly used for 2D data like matrices or multiplication tables.

Nested Loops — Multiplication Table

public class NestedLoops {
    public static void main(String[] args) {
        // Print a 5x5 multiplication table
        for (int i = 1; i <= 5; i++) {
            for (int j = 1; j <= 5; j++) {
                System.out.printf("%4d", i * j);
            }
            System.out.println();
        }
        /*
           1   2   3   4   5
           2   4   6   8  10
           3   6   9  12  15
           4   8  12  16  20
           5  10  15  20  25
        */
    }
}

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Java Loops

for Loop

for-each Loop (Enhanced for)

Nested Loops

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