loops

Why Use Loops?

Loops let you repeat a block of code multiple times without writing it out manually. Java provides three main loop types: for, while, and do-while.

The for Loop

Best used when you know exactly how many times you want to repeat something.

for (int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}

The for loop has three parts separated by semicolons:

   
• Initialization — int i = 1 runs once, before the loop starts

   
• Condition — i <= 5 is checked before every iteration; the loop stops once it's false

   
• Update — i++ runs after every iteration

The while Loop

Best used when you don't know in advance how many times you'll loop — you just keep going until a condition becomes false.

int count = 1;

while (count <= 5) {
    System.out.println("Count: " + count);
    count++;
}

    Warning: Always make sure something inside the loop eventually makes the condition false. Forgetting to update count here would create an infinite loop that never stops.

The do-while Loop

Similar to while, but it checks the condition after running the loop body — guaranteeing the code runs at least once, even if the condition is false from the start.

int count = 1;

do {
    System.out.println("Count: " + count);
    count++;
} while (count <= 5);

The Enhanced for-each Loop

Used to iterate directly over the elements of an array or collection, without needing an index variable.

int[] numbers = {10, 20, 30, 40};

for (int num : numbers) {
    System.out.println(num);
}

break and continue

Two keywords give you finer control inside a loop:

break — exits the loop immediately

for (int i = 1; i <= 10; i++) {
    if (i == 5) {
        break; // stops the loop entirely once i reaches 5
    }
    System.out.println(i);
}
// Output: 1 2 3 4

continue — skips to the next iteration

for (int i = 1; i <= 5; i++) {
    if (i == 3) {
        continue; // skips printing 3, but the loop keeps going
    }
    System.out.println(i);
}
// Output: 1 2 4 5

Nested Loops

A loop can contain another loop inside it — commonly used for working with grids or tables.

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
        System.out.println("i=" + i + ", j=" + j);
    }
}

Choosing the Right Loop

    Coming up next: Arrays — how to store and work with collections of values under a single variable name.