Careeroza

while Loop

Syntax

A while loop repeats a block as long as its condition is true. The condition is checked before each round.

while (condition) {
    // repeated code
}

Example

public class Main {
    public static void main(String[] args) {
        int i = 1;
        while (i <= 5) {
            System.out.println("Round " + i);
            i++;
        }

        // digits of a number
        int n = 9042;
        int digits = 0;
        while (n > 0) {
            n = n / 10;
            digits++;
        }
        System.out.println("Digits: " + digits);
    }
}

Output

Round 1
Round 2
Round 3
Round 4
Round 5
Digits: 4

Note: Always change something inside the loop that makes the condition false eventually. Forgetting i++ creates an infinite loop.

When to Use while

Use while when you do not know in advance how many times to loop, for example "keep retrying until success" or "read until there is no more data".

Example

public class Main {
    public static void main(String[] args) {
        double savings = 10000;
        int years = 0;
        while (savings < 20000) {
            savings = savings * 1.08;   // 8% yearly growth
            years++;
        }
        System.out.printf("Doubled in %d years (Rs. %.2f)%n", years, savings);
    }
}

Output

Doubled in 10 years (Rs. 21589.25)