不用synchronized和lock能实现线程安全的单例吗？

饿汉式单例模式天生线程安全，类加载的时候初始化一次对象即可

public class Singleton {
    private static final AtomicReference<Singleton> INSTANCE = new AtomicReference<Singleton>(); 

    private Singleton() {}

    public static Singleton getInstance() {
        for (;;) {
            Singleton singleton = INSTANCE.get();
            if (null != singleton) {
                return singleton;
            }

            singleton = new Singleton();
            if (INSTANCE.compareAndSet(null, singleton)) {
                return singleton;
            }
        }

}

}