Java Do-While Loop — Java Technical Interview Questions & Answers

Java Do-While Loop

Java Do-While Loop

  • do-while runs the body first, then checks. So it always runs at least once. Shape: do { body } while (condition); — the semicolon at the end is required.
  • Order: body → check → maybe body again. Use it when you must do something once before you can decide: show a menu, ask for input once.
  • while can skip the body completely. do-while cannot. Freshers forget the semicolon after while (condition) and get a compile error.
  • Let's take this on the board with one tiny Main class — no extra files. Java Do-While Loop — output: 1 then 2 then 3. do-while runs the body first, then checks. Even if i started at 9, one print would still happen. Start from main, go line by line, and stop at each print. That output is the proof for Do-While Loop.
   body first
         │
         ▼
   check ── true → body again
         │ false
         ▼
        stop

Technical Interview Tip: One line: do-while guarantees one execution. Show a menu loop.

Code Examples for Java Do-While Loop

Example

// Java Do-While — prints 1, 2, 3
public class Main {
  public static void main(String[] args) {
    int i = 1;
    do {
      System.out.println(i);
      i++;
    } while (i <= 3);
  }
}

Java Do-While Loop — output: 1 then 2 then 3. do-while runs the body first, then checks. Even if i started at 9, one print would still happen.

How to Explain Java Do-While Loop to an Interviewer

How many times does do-while run at minimum?

At least once

What is the order?

Body first Then check

What do people forget?

Semicolon after while (condition)