Loop execution flow in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested loops with break

What is the output of the following Java code snippet?

Java

public class Main {
    public static void main(String[] args) {
        for (int i = 1; i <= 3; i++) {
            for (int j = 1; j <= 3; j++) {
                if (j == 2) {
                    break;
                }
                System.out.print(i + "-" + j + " ");
            }
        }
    }
}

A 1-1 1-2 1-3 2-1 2-2 2-3 3-1 3-2 3-3

B 1-1 1-2 2-1 2-2 3-1 3-2

C 1-1 2-1 3-1 3-2

D 1-1 2-1 3-1

💡 Hint

Remember that break exits the innermost loop immediately.

The inner loop breaks when j == 2, so only j=1 prints for each i. Thus output is "1-1 2-1 3-1 ".

❓ Predict Output

intermediate

Output of while loop with continue

What will be printed by this Java code?

Java

public class Main {
    public static void main(String[] args) {
        int i = 0;
        while (i < 5) {
            i++;
            if (i == 3) {
                continue;
            }
            System.out.print(i + " ");
        }
    }
}

A 2 3 4 5

B 1 2 3 4 5

C 1 2 4 5

D 1 2 3 4

💡 Hint

The continue skips the print when i equals 3.

When i is 3, continue skips the print statement, so 3 is not printed. All other values from 1 to 5 print.

🔧 Debug

advanced

Identify the error in for loop increment

What error will this Java code produce when run?

Java

public class Main {
    public static void main(String[] args) {
        for (int i = 0; i < 5; i = i++) {
            System.out.print(i + " ");
        }
    }
}

A Infinite loop printing 0 repeatedly

B Compilation error: invalid increment expression

C Prints 0 1 2 3 4

D Runtime exception: ArrayIndexOutOfBoundsException

💡 Hint

Look carefully at the increment expression i = i++.

The expression i = i++ does not change i because i++ returns the original value before increment. So i stays 0, causing an infinite loop.

❓ Predict Output

advanced

Output of for loop with multiple variables

What is the output of this Java code?

Java

public class Main {
    public static void main(String[] args) {
        for (int i = 0, j = 5; i < j; i++, j--) {
            System.out.print(i + "-" + j + " ");
        }
    }
}

A 0-5 1-4 2-3 3-2

B 0-5 1-4 2-3

C 0-5 1-4 2-3 3-2 4-1

D 0-5 1-4

💡 Hint

The loop stops when i is no longer less than j.

The loop runs while i < j. Iterations: (0,5), (1,4), (2,3). When i=3 and j=2, condition fails, loop stops.

🧠 Conceptual

expert

Number of iterations in nested loops with dependent conditions

Consider the following Java code. How many times will the innermost print statement execute?

Java

public class Main {
    public static void main(String[] args) {
        int count = 0;
        for (int i = 1; i <= 4; i++) {
            for (int j = i; j <= 4; j++) {
                count++;
            }
        }
        System.out.println(count);
    }
}

A 10

B 16

C 20

D 8

💡 Hint

Count how many times j runs for each i.

For i=1, j=1..4 (4 times); i=2, j=2..4 (3 times); i=3, j=3..4 (2 times); i=4, j=4..4 (1 time). Total 4+3+2+1=10.