多线程死锁现象

package demo.thread;

class DeadLock1 extends Thread {
    DeadLock1(String name) {
        super(name);
    }

    public void run() {
        if ("f".equals(getName())) {
            synchronized ("遥控器") {
                System.out.println(getName() + "拿到了遥控器");
                synchronized ("电池") {
                    System.out.println(getName() + "拿到了电池和遥控器，开着空调爽歪歪");
                }
            }
        } else if ("m".equals(getName())) {
            synchronized ("电池") {
                System.out.println(getName() + "拿到了电池");
                synchronized ("遥控器") {
                    System.out.println(getName() + "拿到了电池和遥控器，开着空调爽歪歪");
                }
            }
        }
    }
}

class DeadLock2 implements Runnable {
    Object obj = new Object();
    private int num = 100;

    public void run() {
        if ("a".equals(Thread.currentThread().getName()))
            while (true) {
                synchronized (obj) {        //a进来锁上obj                    1
                    show();                //a进不去this的锁（非静态方法的锁是this）       3
                }
            }
        else if ("b".equals(Thread.currentThread().getName()))
            while (true)
                this.show();
    }

    private synchronized void show() {
        //b进来锁上this                                                     2
        synchronized (obj) {          //b进不去obj的锁                           4
            if (num > 0) {
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                }
                System.out.println(Thread.currentThread().getName() + ".....sale...." + num--);
            }
        }
    }
}

class DeadLockTest {
    public static void main(String[] args) {
        DeadLock1 f = new DeadLock1("f");
        DeadLock1 m = new DeadLock1("m");
         f.start();
        m.start();

        DeadLock2 d = new DeadLock2();
        Thread a = new Thread(d, "a");
        Thread b = new Thread(d, "b");
        a.start();
        b.start();
    }
}
/*死锁现象出现 的根本原因：
	1. 存在两个或者两个以上的线程。
	2. 存在两个或者两个以上的共享资源。*/

f拿到了遥控器
f拿到了电池和遥控器，开着空调爽歪歪
m拿到了电池
m拿到了电池和遥控器，开着空调爽歪歪
a…sale…100
a…sale…99
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a…sale…1
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