package cn.sasa.demo4;
public class ThreadDemo {
public static void main(String[] args){
DeadLockRunnable dead = new DeadLockRunnable();
Thread t0 = new Thread(dead);
Thread t1 = new Thread(dead);
Thread t2 = new Thread(dead);
t0.start();
t1.start();
t2.start();
/**
* 线程中出现同步的嵌套，容易发生死锁
*
* Thread-1---if---locka---
* Thread-1---if---lockb---
* Thread-1---else---lockb---
* Thread-0---if---locka---
* 发生死锁
*/
}
}
package cn.sasa.demo4;
public class DeadLockRunnable implements Runnable{
/**
* 线程嵌套容易发生死锁，线程出现无限等待
*/
public void run() {
int flag = 100;
while(flag > 0) {
if(flag % 2 == 0) {
//先进入A同步，再进B同步
synchronized(Locka.locka) {
System.out.println(Thread.currentThread().getName() + "---if---locka---");
synchronized (Lockb.lockb) {
System.out.println(Thread.currentThread().getName() + "---if---lockb---");
}
}
}else {
//先进入B同步，再进A同步
synchronized(Lockb.lockb) {
System.out.println(Thread.currentThread().getName() + "---else---lockb---");
synchronized (Locka.locka) {
System.out.println(Thread.currentThread().getName() + "---else---locka---");
}
}
}
flag--;
}
}
}
package cn.sasa.demo4;
public class Locka {
//单例 对象只允许创建一次
private Locka() {}
public static final Locka locka = new Locka();
}
package cn.sasa.demo4;
public class Lockb {
private Lockb() {}
public static final Lockb lockb = new Lockb();
}
