JavaCore java

While Loop in Java

Why While Loop?

When we want to repeat a task multiple times until a condition is true.
Syntax:

while (condition) {
    // statements
}

Loop continues until the condition becomes false.

Example 1 – Infinite Loop

public class Demo {
    public static void main(String[] args) {
        while (true) {
            System.out.println("Hi");
        }
    }
}

👉 Prints Hi continuously until memory runs out.

Example 2 – Loop with Counter

int i = 1;
while (i <= 4) {
    System.out.println("Hi " + i);
    i++;
}
System.out.println("Bye " + i);

👉 Output:

Hi 1
Hi 2
Hi 3
Hi 4
Bye 5

Example 3 – Nested While Loop

int i = 1;
while (i <= 4) {
    System.out.println("Hi " + i);

    int j = 1;
    while (j <= 3) {
        System.out.println("Hello " + j);
        j++;
    }

    i++;
}

👉 Output:

Hi 1
Hello 1
Hello 2
Hello 3
Hi 2
Hello 1
Hello 2
Hello 3
Hi 3
Hello 1
Hello 2
Hello 3
Hi 4
Hello 1
Hello 2
Hello 3

Key Notes

Initialization must be done before loop (e.g., int i = 1).
Condition checked before each iteration.
Update (e.g., i++) ensures loop moves toward termination.
Can be nested (loop inside loop).
Without proper condition/update → may lead to infinite loop.

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Why While Loop?Example 1 – Infinite Loop Example 2 – Loop with Counter Example 3 – Nested While Loop Key Notes