钉钉为什么会有多个线程同时获取到锁？

钉钉为什么会有多个线程同时获取到锁？package org.idle.fish;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

/*
*/
public class CustomLock {

private static final AtomicReference<Thread> STATE = new AtomicReference<>();

public void lock() {
    // 自旋，直到没有线程持有当前锁
    while (!STATE.compareAndSet(null, Thread.currentThread())) {
    }
    System.out.println(Thread.currentThread().getName() + "获取锁成功");
}

public void unLock() {
    // 释放锁
    STATE.compareAndSet(Thread.currentThread(), null);
    System.out.println(Thread.currentThread().getName() + "解锁成功");
}

}

class Test {
public static void main(String[] args) throws InterruptedException {
CustomLock customLock = new CustomLock();
for (int i = 0; i < 10; i++) {
new Thread(() -> {
customLock.lock();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
customLock.unLock();
}
}).start();
}
TimeUnit.MINUTES.sleep(1);
}
}