Livelock vs Deadlock in Java

Direct Answer

In deadlock, threads cannot progress because they wait in a dependency cycle. In livelock, threads keep changing state or retrying in response to one another but still complete no useful work. Livelock often consumes CPU, but CPU level and Java thread state are symptoms, not definitions.

Code Example

public class LivelockDemo {
    static volatile boolean aYields = true;
    static volatile boolean bYields = true;

    public static void main(String[] args) {
        // Each thread keeps stepping aside for the other -> active, but no progress
        Runnable a = () -> {
            while (bYields) { Thread.onSpinWait(); } // busy-waiting, not blocked
            System.out.println("A proceeds");
        };
        Runnable b = () -> {
            while (aYields) { Thread.onSpinWait(); }
            System.out.println("B proceeds");
        };
        new Thread(a).start();
        new Thread(b).start();
    }
}

In deadlock both threads sit idle in BLOCKED. In livelock both run flat out yet neither finishes — fix it by breaking symmetry with randomized backoff or lock ordering.

Common Mistakes & Pitfalls

• Using the terms interchangeably: calling every stuck condition "deadlock" misses that livelock is a distinct problem with different symptoms.
• Not knowing the hallway analogy: it is the standard explanation interviewers expect — not having it ready looks unprepared.
• Forgetting CPU usage: the key differentiator is that livelock burns CPU while deadlock does not — leaving this out misses the practical impact.