过多的同步方法可能造成死锁。 MyThread：主程序。 Test1：卖家。 Test2：买家。 场景：一手给钱，一手给货，两者都拿着各自的锁不松手。造成死锁，无输出。

public class MyThread{
    public static void main(String[] args) throws InterruptedException {
        Object goods = new Object();
        Object money = new Object();
        Test1 t1 = new Test1(goods, money);
        Test2 t2 = new Test2(goods, money);
        new Thread(t1).start();
        new Thread(t2).start();
    }
}


class Test1 implements Runnable {
    Object goods;
    Object money;
    public Test1(Object goods, Object money) {
        this.goods = goods;
        this.money = money;
    }
    @Override
    public void run() {
        while(true) {
            test();
        }
    }
    public void test() {
        synchronized(goods) {
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            synchronized (money) {

                
            }
            //注：这里已经有了商品，即Test1是卖家，需要给钱才能给货（goods的锁）。
            System.out.println("一手给钱");
        }
    }
}


class Test2 implements Runnable {
    Object goods;
    Object money;
    public Test2(Object goods, Object money) {
        this.goods = goods;
        this.money = money;
    }
    @Override
    public void run() {
        while(true) {
            test();
        }
    }
    public void test() {
        synchronized(money) {
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            synchronized (goods) {

                
            }
            //注：这里已经有了钱，即Test2是买家，需要给货才能给钱（money的锁）。
            System.out.println("一手给货");
        }
    }
}