解决单例模式中懒汉式不支持高并发，饿汉式不支持懒加载问题最简单方法——基于枚举类型的单例实现

import java.util.concurrent.atomic.AtomicInteger;
public class Single {
    private AtomicInteger count = new AtomicInteger(3);
    public int getReduce(){
        return count.decrementAndGet();
    }
}

public enum PhoneEnum {
    PHONE_ENUM;
    private Single instance;
    PhoneEnum() {
        instance = new Single();
    }
    public Single getInstance() {
        return instance;
    }
}

public class BingFa {
    public static void main(String[] args) {
        // 创建3个线程，线程里面进行加操作
        for (int i = 0; i < 3; i++) {
            new Thread(() -> {
                Single instance = PhoneEnum.PHONE_ENUM.getInstance();
                int reduce = instance.getReduce();
                System.out.println(Thread.currentThread().getName()+
                          "线程抢到了手机，剩余手机数量"+"-----"+reduce);
            }, String.valueOf(i)).start();
        }
    }
}