Java自旋锁（Spin Lock）是一种用于多线程同步的锁机制，通过反复检查某个条件（通常是一个共享变量的状态）而不是挂起线程来实现锁的获取。自旋锁的核心思想是让线程在尝试获取锁时保持活动状态，即进行“自旋”，以期望在短时间内锁能够被释放，从而避免线程上下文切换的开销。

import java.util.concurrent.atomic.AtomicBoolean;

public class SpinLock {
    private final AtomicBoolean lock = new AtomicBoolean(false);

    public void lock() {
    	// lock.compareAndSet(expectedValue, newValue)
    	// if expectedValue equals to initial value false will return true, else return false
        while (!lock.compareAndSet(false, true)) {
            // 自旋等待锁释放
        }
    }

    public void unlock() {
        lock.set(false);
    }

    public static void main(String[] args) {
        SpinLock spinLock = new SpinLock();

        Runnable task = () -> {
            System.out.println(Thread.currentThread().getName() + " attempting to acquire lock");
            spinLock.lock();
            try {
                System.out.println(Thread.currentThread().getName() + " acquired lock");
                // 执行临界区代码
            } finally {
                spinLock.unlock();
                System.out.println(Thread.currentThread().getName() + " released lock");
            }
        };

        Thread thread1 = new Thread(task);
        Thread thread2 = new Thread(task);

        thread1.start();
        thread2.start();
    }
}