Livelock and Starvation in Multithreaded Java Programs: Causes and Prevention

While deadlocks are well-known in concurrent programming, livelock and starvation are equally problematic — often harder to detect but just as disruptive. They prevent progress, reduce responsiveness, and complicate debugging.

This tutorial covers how livelocks and starvation occur, with examples, prevention techniques, and best practices in Java concurrency.

🔄 What Is Livelock?

Livelock is a state where two or more threads continually change state in response to each other but fail to make actual progress.

Real-world analogy

Two people step aside repeatedly to let the other pass through a doorway — both polite, but nobody moves forward.

❄️ What Is Starvation?

Starvation occurs when a thread is perpetually denied access to resources because other threads are prioritized.

Real-world analogy

In a cafeteria line, new people constantly cut in front of someone waiting — that person may never get food.

🧵 Thread Lifecycle and These Issues

Both livelock and starvation impact the RUNNABLE and BLOCKED/WAITING stages of a thread’s lifecycle.

States: NEW → RUNNABLE → RUNNING → WAITING/BLOCKED → TERMINATED

🧪 Java Example of Livelock

class Livelock {
    static class Spoon {
        private Diner owner;
        public Spoon(Diner owner) { this.owner = owner; }
        public synchronized void use() {
            System.out.println(owner.name + " has the spoon!");
        }
        public Diner getOwner() { return owner; }
        public void setOwner(Diner diner) { this.owner = diner; }
    }

    static class Diner {
        private String name;
        public Diner(String name) { this.name = name; }
        public String getName() { return name; }
        public boolean isHungry = true;

        public void eatWith(Spoon spoon, Diner partner) {
            while (isHungry) {
                if (spoon.getOwner() != this) {
                    try { Thread.sleep(1); } catch (InterruptedException e) {}
                    continue;
                }

                if (partner.isHungry) {
                    System.out.println(name + " gives spoon to " + partner.getName());
                    spoon.setOwner(partner);
                    continue;
                }

                spoon.use();
                isHungry = false;
                System.out.println(name + " is done eating.");
                spoon.setOwner(partner);
            }
        }
    }
}

Both diners keep giving the spoon back — and nobody eats.

🧪 Java Example of Starvation

ExecutorService executor = Executors.newFixedThreadPool(1);

// Long-running thread
executor.submit(() -> {
    while (true) {
        // monopolizing CPU
    }
});

// Starved task
executor.submit(() -> System.out.println("May never execute!"));

The long-running task prevents the second from executing.

📉 Causes of Livelock and Starvation

Livelock Causes

Mutual politeness (threads constantly yielding)
Retry loops with shared state
Faulty coordination logic

Starvation Causes

Priority inversion (low-priority threads blocked by high ones)
Unfair locks (ReentrantLock without fairness)
Thread monopolization

🛠 How to Prevent Livelock

Limit retry logic with Thread.yield() or exponential backoff
Break symmetry in coordination algorithms
Introduce timeouts in retry loops
Avoid circular dependencies between threads

🛠 How to Prevent Starvation

Use fair locks (new ReentrantLock(true))
Avoid infinite loops in shared thread pools
Allow CPU time sharing using Thread.sleep() or yielding
Prefer Executors that distribute tasks fairly

📌 What's New in Java Concurrency (8–21)

Java 8: CompletableFuture, parallel streams
Java 9: Flow API for reactive programming
Java 11: Enhancements to async tasks and futures
Java 21: Structured concurrency, virtual threads, ScopedValue

✅ Best Practices

Use bounded thread pools to prevent resource starvation
Always test concurrency with load and contention
Prefer declarative concurrency over manual thread management
Document retry and coordination logic clearly

❓ FAQ

Is livelock the same as deadlock?
No — livelock allows threads to run but not progress; deadlock halts them.
Does synchronized cause starvation?
It can, especially if long-held locks delay others.
Can fair locks prevent starvation?
Yes — fair locks process threads in request order.
Are livelocks more likely with ReentrantLock?
Only if retry loops or yielding logic is poorly implemented.
Is Thread.yield() reliable?
Not always — it’s a hint to the scheduler, not a guarantee.
What tools help detect livelock?
Profilers, logs, and thread dumps showing frequent state changes.
How can we simulate starvation in testing?
Use low-priority threads alongside CPU-intensive tasks.
Can thread pools cause starvation?
Yes — especially if tasks hog the threads and don’t terminate.
Is livelock common in practice?
Less common than deadlocks but harder to detect.
Do virtual threads prevent starvation?
They help, but logical flaws can still cause it.

🧾 Conclusion and Key Takeaways

Livelocks and starvation silently degrade performance and reliability.
They differ from deadlocks but are just as dangerous.
Understand thread coordination patterns to avoid them.
Use fairness policies, bounded retries, and well-designed concurrency tools.

Preventing livelocks and starvation is key to writing responsive and maintainable multithreaded Java applications.