DoWhileLoop.md

Do-While Loops in Java

Introduction

A do-while loop is a control flow statement that allows code to be executed repeatedly based on a given boolean condition. Unlike a while loop, a do-while loop is guaranteed to execute at least once because the condition is evaluated after the loop body.

Syntax

do {
    // code to be executed
} while (condition);

• Loop Body: This is the block of code that will be executed at least once and then repeatedly as long as the condition is true.
• Condition: This is evaluated after each iteration. If the condition is true, the loop body is executed again. If it is false, the loop terminates.

Use Cases

• Executing code at least once: When you need to ensure that the loop body is executed at least once, a do-while loop is the right choice.
• User input validation: Often used in scenarios where user input needs to be validated and the prompt should be shown at least once.
• Menu-driven programs: Useful in creating menu-driven programs where the menu should be displayed at least once.

Example

public class DoWhileLoopExample {
    public static void main(String[] args) {
        int i = 1;
        // Print numbers from 1 to 5
        do {
            System.out.println(i);
            i++;
        } while (i <= 5);
    }
}

Noticing the Need for a Do-While Loop

You might notice the need for a do-while loop when:

• You have a task that must be executed at least once before any condition is checked.
• You need to repeatedly prompt the user for input until a valid response is received.

Difference Between While and Do-While

• Execution Guarantee: A while loop checks the condition before executing the loop body, so it may not execute at all if the condition is false initially. A do-while loop, on the other hand, executes the loop body at least once before checking the condition.
• Syntax: In a while loop, the condition is placed at the beginning, whereas in a do-while loop, the condition is placed at the end.

While Loop Example

public class WhileLoopExample {
    public static void main(String[] args) {
        int i = 1;
        // Print numbers from 1 to 5
        while (i <= 5) {
            System.out.println(i);
            i++;
        }
    }
}

Do-While Loop Example

public class DoWhileLoopExample {
    public static void main(String[] args) {
        int i = 1;
        // Print numbers from 1 to 5
        do {
            System.out.println(i);
            i++;
        } while (i <= 5);
    }
}

In summary, choose a do-while loop when you need the loop body to execute at least once, and a while loop when the loop body should only execute if the condition is initially true.