Do-While & When to Use It
Run the loop body at least once with do-while. Learn syntax, use-cases, differences from while, and common pitfalls.
Do-While & When to Use It is a free Java Academy lesson on CoddyKit. This is lesson 2 of 2. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, and your progress syncs across the web and the CoddyKit app. The Java Academy course includes 2 lessons in total.
Do-While Concept
do-while runs the body before checking the condition. So it runs at least once.
Syntax
Syntax
int i = 0;
do {
// work
i = i + 1;
} while (i < 3);The semicolon after while (...) is required.
When to Use
Use when you must perform the action once, then decide to continue. Examples: showing a menu once, running a first step before checking a flag.
Compare with while
do-while vs while
whilechecks first; might run zero timesdo-whileruns once, then checks- Pick the one that matches your need
Pitfalls
Pitfalls
- Forgetting the semicolon after
while (cond) - Not updating the loop variable
- Condition never becomes false → infinite loop
Do-While Demo
Run it: First loop prints n = 0,1,2. Second loop prints once even though the condition is false.
public class Main {
public static void main(String[] args) {
int n = 0;
// Runs at least once
do {
System.out.println("n is " + n);
n = n + 1;
} while (n < 3);
// Condition false initially: still runs once
int x = 10;
do {
System.out.println("Runs once even though x < 0 is false");
} while (x < 0);
}
}
Runs Once
Quick check: Which snippet prints "Run once" exactly once when the condition starts false?
Recap & Next
Recap: You learned do-while syntax, when to use it, how it differs from while, and common pitfalls.
Next: Practice set to choose between while and do-while, and refactor loops.
Learn Java with an AI tutor — free
Write and run real code in your browser, get instant help from a 24/7 AI tutor, and pick up where you left off on the web or in the app.
- Courses
- 104
- Lessons
- 374
Frequently Asked Questions
Is the “Do-While & When to Use It” lesson free?
Yes — the full text of “Do-While & When to Use It” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO. The Java Academy course includes 2 lessons in total.
What will I learn in “Do-While & When to Use It”?
Run the loop body at least once with do-while. Learn syntax, use-cases, differences from while, and common pitfalls. You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Java Academy?
No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 2.
How long does the “Do-While & When to Use It” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Java Academy lesson?
Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- While Loop Basics
- Do-While & When to Use It