javaLogic errorMedium

Unexpected Behavior in Traffic Light State Transitions

Time: 0:00

BugFind the bug and fix the code

What it should do

Simulate traffic light state transitions. Example: transitionTrafficLight('GREEN') -> 'YELLOW'

What happens instead

Traffic light transitions to unexpected states during simulation.

public class TrafficLight {
    enum State { RED, YELLOW, GREEN }

    public static String transitionTrafficLight(String currentState) {
        String nextState = "INVALID";
        switch (currentState) {
            case "RED":
                nextState = "GREEN";
            case "YELLOW":
                nextState = "RED";
            case "GREEN":
                nextState = "YELLOW";
            default:
                nextState = "INVALID";
        }
        return nextState;
    }
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

🏆 0 hints = Flawless Solve

Think & Test Cooldown

2:00 remaining

Take a moment to read the bug symptom and trace the code with Run & Check before unlocking Hint 1.

Hint 2

Unlocks after Hint 1

Hint 3

Unlocks after Hint 2

This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

<iframe src="https://trybughunt.com/embed/e1a7d137-9871-4f21-ba81-b43aa9bcb9fd" title="Debugging challenge: Unexpected Behavior in Traffic Light State Transitions" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe> <p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/e1a7d137-9871-4f21-ba81-b43aa9bcb9fd">TryBugHunt</a></p>

public class TrafficLight { enum State { RED, YELLOW, GREEN } public static String transitionTrafficLight(String currentState) { String nextState = "INVALID"; switch (currentState) { case "RED": nextState = "GREEN"; case "YELLOW": nextState = "RED"; case "GREEN": nextState = "YELLOW"; default: nextState = "INVALID"; } return nextState; } }

Unexpected Behavior in Traffic Light State Transitions

What it should do

What happens instead

More logic errors to practise

Unexpected Behavior in Traffic Light State Transitions

What it should do

What happens instead

More logic errors to practise