Java Do-While Loop: Exit-Controlled Execution & Interactive Menus

The do-while loop is an exit-controlled loop. Unlike the for and while loops that evaluate their conditions at the entry gate, the do-while loop executes its statement body first, and only evaluates the continuation condition at the end of each iteration.

Syntax and Key Structural Rule

// Do-While Syntax (Notice mandatory trailing semicolon!)
do {
    // Statements executed at least once
    // Update expression
} while (boolean_condition);

Practical Example: Interactive Menu-Driven System

A ubiquitous assignment in BCA and CS lab exams is building a menu-driven program that runs until the user explicitly enters an exit command:

import java.util.Scanner;

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

        do {
            System.out.println("
=== VEEWOM BANKING MENU ===");
            System.out.println("1. Check Account Balance");
            System.out.println("2. Deposit Funds");
            System.out.println("3. Withdraw Funds");
            System.out.println("4. Exit Application");
            System.out.print("Enter your selection (1-4): ");
            
            choice = scanner.nextInt();

            switch (choice) {
                case 1 -> System.out.println("Your Current Balance: $5,420.00");
                case 2 -> System.out.println("Deposit window opened.");
                case 3 -> System.out.println("Withdrawal processing...");
                case 4 -> System.out.println("Thank you for using Veewom Banking. Goodbye!");
                default -> System.out.println("Invalid selection! Please enter a number 1 to 4.");
            }
        } while (choice != 4); // Loop repeats until user picks 4

        scanner.close();
    }
}

Side-by-Side Comparison: While vs. Do-While

int count = 10;
do {
    System.out.print(count + " ");
    count++;
} while (count < 5);