Java Loops
for, while, do-while

Introduction to Loops in Java

Imagine writing a task 100 times manually. Sounds exhausting, right? Loops in Java are designed to help you automate repetitive actions with control. In this tutorial, we’ll walk through all types of Java loops, when to use them, and how to write and understand their outputs step-by-step.

Types of Loops in Java

Java offers three primary looping constructs:

• for loop
• while loop
• do-while loop

Let’s explore each with real-life examples and logic breakdowns.

Java for Loop

The for loop is best when you know how many times you want to repeat a block of code. It’s concise and powerful.

public class ForLoopExample {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Hello Java " + i);
        }
    }
}

Hello Java 1
Hello Java 2
Hello Java 3
Hello Java 4
Hello Java 5

Explanation

• int i = 1; → Initializes the loop variable
• i <= 5; → Checks if the loop should continue
• i++ → Increments i after each iteration

This loop runs 5 times, printing a friendly message each time with the count.

Java while Loop

Use a while loop when you want the loop to run as long as a condition remains true — but you may not know in advance how many times.

public class WhileLoopExample {
    public static void main(String[] args) {
        int i = 1;
        while (i <= 3) {
            System.out.println("Counter: " + i);
            i++;
        }
    }
}

Counter: 1
Counter: 2
Counter: 3

Explanation

The loop continues as long as i <= 3. Notice how you must manually initialize and increment i — this gives you more control but requires careful handling to avoid infinite loops.

Java do-while Loop

A do-while loop guarantees that the block runs at least once — even if the condition is false initially.

public class DoWhileExample {
    public static void main(String[] args) {
        int i = 1;
        do {
            System.out.println("Do-While Count: " + i);
            i++;
        } while (i <= 2);
    }
}

Do-While Count: 1
Do-While Count: 2

Explanation

Unlike the while loop, this format ensures the loop body executes at least once before checking the condition.

Infinite Loops

Loops without a termination condition can run forever — either accidentally or by design (like servers listening for requests).

// WARNING: This is an infinite loop
while (true) {
    System.out.println("Running endlessly...");
}

Be cautious! Infinite loops can freeze your program if not intentionally used.

Break and Continue

Java loops can be further controlled using break and continue statements.

Using break

for (int i = 1; i <= 5; i++) {
    if (i == 3) break;
    System.out.println(i);
}

1
2

Using continue

for (int i = 1; i <= 5; i++) {
    if (i == 3) continue;
    System.out.println(i);
}

1
2
4
5

break exits the loop early; continue skips the current iteration and moves to the next.

Nested Loops

Loops inside loops — useful for multidimensional data or repeated patterns.

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 2; j++) {
        System.out.println("i = " + i + ", j = " + j);
    }
}

i = 1, j = 1
i = 1, j = 2
i = 2, j = 1
i = 2, j = 2
i = 3, j = 1
i = 3, j = 2

When to Use Which Loop?

Loop Type	Best For
for	Known number of repetitions
while	Unknown repetitions, condition-controlled
do-while	Always execute at least once