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 — 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, one of 2 lessons in the course, and your progress syncs across the web and the CoddyKit app.
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.
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, and the Java Academy course includes 2 lessons in total. 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.
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; this is — lesson 2 of 2, so you can start here or from the beginning and move at your own pace.
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