Java Do…While Loop

The do...while loop is similar to the while loop, but with one important difference:

👉 The code block executes at least once, even if the condition is false, because the condition is checked after the loop executes.

Syntax

📌 Note: A semicolon ; is required after the condition.

Example 1: Basic do…while Loop

📌 Output:

Example 2: Condition False at First

Even when the condition is false, the block executes once:

📌 Output:

Example 3: User Input Loop (Practical Use Case)

import java.util.Scanner;

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

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

System.out.println("Thank you! You entered: " + number);
}
}

import java.util.Scanner;

public class Main {

public static void main(String[] args) {

Scanner input = new Scanner(System.in);

int number;

do {

System.out.print("Enter a number greater than 0: ");

number = input.nextInt();

} while (number <= 0);

System.out.println("Thank you! You entered: " + number);

}

📌 This forces input until user enters a valid number.

🔍 Key Difference: `while` vs `do...while`

Feature	`while` Loop	`do...while` Loop
Condition checked	Before execution	After execution
Executes at least once?	❌ No	✅ Yes
Best used when	Unsure if loop should run	Loop must run at least once

👍 Summary

do...while ensures code runs at least one time.
Useful for input validation or cases requiring an initial action.

Java Do…While Loop