SummerVocation_Learning--java的线程死锁

 
public class Test_DeadLock implements Runnable {
 
    public int flag = 1;
    static Object o1 = new Object(),o2 = new Object();
    public void run() {
        System.out.println("flag= " + flag);
        if (flag == 1) {
            synchronized (o1) {  //o1锁定
                try {
                    Thread.sleep(500);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            synchronized (o2) { //只要再锁定o2，就能打印出1.
                System.out.println("1"); //但是o2被另一个线程锁定了，所以打印不出1.
                }
            }
        }
        if (flag == 0) {
            synchronized (o2) { //锁定o2
                try {
                    Thread.sleep(500);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            synchronized (o1) {  //只要再等待锁定o1，就能打印出0.
                    System.out.println("0"); //但是o1另一个线程锁定，无法执行。两个线程被锁死，谁都无法完成执行。
                }
            }
        }
    }
    
    public static void main(String[] args) {
        Test_DeadLock t1 = new Test_DeadLock();
        Test_DeadLock t2 = new Test_DeadLock();
        t1.flag = 1;
        t2.flag = 0;
        Thread t11 = new Thread(t1);
        Thread t21 = new Thread(t2);
        t11.start(); t21.start();
 
    }
    /*
     * flag= 1
       flag= 0
                两个线程产生死锁，synchronized的输出语句未被执行。
     */
 
}