package dev.elaine.jvmlab;

import java.util.concurrent.CountDownLatch;

public final class DeadlockSample {
    private static final Object FIRST_LOCK = new Object();
    private static final Object SECOND_LOCK = new Object();

    private DeadlockSample() {
    }

    public static void main(String[] args) throws InterruptedException {
        CountDownLatch firstLocksHeld = new CountDownLatch(2);
        startWorker("锁顺序-A-B", FIRST_LOCK, SECOND_LOCK, firstLocksHeld);
        startWorker("锁顺序-B-A", SECOND_LOCK, FIRST_LOCK, firstLocksHeld);
        System.out.println("PID=" + ProcessHandle.current().pid());
        Thread.currentThread().join();
    }

    private static void startWorker(String name, Object first, Object second, CountDownLatch latch) {
        Thread.ofPlatform().name(name).start(() -> {
            synchronized (first) {
                latch.countDown();
                await(latch);
                synchronized (second) {
                    throw new AssertionError("不应执行到这里");
                }
            }
        });
    }

    private static void await(CountDownLatch latch) {
        try {
            latch.await();
        } catch (InterruptedException exception) {
            Thread.currentThread().interrupt();
        }
    }
}