Do–while loop in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple do–while loop

What is the output of the following Java code?

Java

int count = 1;
do {
    System.out.print(count + " ");
    count++;
} while (count <= 3);

A 1 2

B 1 2 3

C 2 3

D No output

💡 Hint

Remember, do–while executes the loop body at least once before checking the condition.

The loop starts with count = 1, prints it, then increments. It repeats while count <= 3, so it prints 1, 2, and 3.

❓ Predict Output

intermediate

Value of variable after do–while loop

What is the value of variable x after this code runs?

Java

int x = 5;
do {
    x -= 2;
} while (x > 0);

A -1

B 1

C 0

D 3

💡 Hint

Check how x changes each loop and when the loop stops.

x starts at 5, then subtracts 2 each time: 5->3->1->-1. The loop stops when x <= 0, so final x is -1.

🔧 Debug

advanced

Identify the error in this do–while loop

What error does this code produce when compiled?

Java

int i = 0;
do {
    System.out.println(i);
    i++
} while (i < 3);

A SyntaxError: missing parentheses in while

B RuntimeException: infinite loop

C No error, prints 0 1 2

D SyntaxError: missing semicolon

💡 Hint

Look carefully at the line before the while condition.

The line 'i++' is missing a semicolon, causing a syntax error.

❓ Predict Output

advanced

Output with break inside do–while loop

What is the output of this code?

Java

int n = 1;
do {
    if (n == 3) break;
    System.out.print(n + " ");
    n++;
} while (n <= 5);

A 1 2 3 4 5

B 1 2 3

C 1 2

D No output

💡 Hint

The break stops the loop when n equals 3.

The loop prints 1 and 2, then when n is 3, it breaks before printing.

🧠 Conceptual

expert

Minimum iterations of do–while vs while loop

Which statement is true about do–while loops compared to while loops?

A A do–while loop always executes its body at least once, even if the condition is false initially.

B A do–while loop may never execute its body if the condition is false initially.

C A while loop always executes its body at least once, even if the condition is false initially.

D Both do–while and while loops execute their body the same number of times regardless of the condition.

💡 Hint

Think about when the condition is checked in each loop type.

A do–while loop checks the condition after running the body once, so it always runs at least once. A while loop checks before running.