Do While Loop

Lecture 26:- Do While Loop

In Java, the do-while loop is similar to the while loop, but with one key difference: the do-while loop guarantees that the block of code will be executed at least once, regardless of whether the condition is true or false. After the initial execution, the loop will continue to execute as long as the specified condition remains true. The basic syntax of the do-while loop is as follows:

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do {
    // Code to be executed at least once
} while (condition);

Here's an example of using a do-while loop to take input from the user until a positive number is entered:

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import java.util.Scanner;

public class DoWhileLoopExample {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int number;

        do {
            System.out.print("Enter a positive number: ");
            number = scanner.nextInt();
        } while (number <= 0);

        System.out.println("You entered a positive number: " + number);
        scanner.close();
    }
}

Example usage:

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Enter a positive number: -5
Enter a positive number: 0
Enter a positive number: 10
You entered a positive number: 10

In the example above, the do-while loop ensures that the prompt for user input (Enter a positive number:) is displayed at least once. After the initial execution, the loop checks whether the entered number is less than or equal to 0. If the condition is true (i.e., a non-positive number is entered), the loop continues to prompt for input until a positive number is entered.

The do-while loop is particularly useful in situations where you want to execute a block of code at least once, regardless of the condition's initial value. Just like the while loop, it's essential to ensure that the condition eventually becomes false to avoid an infinite loop.

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