死锁

public class DeadLock implements Runnable {public int flag = 1;static Object o1 = new Object(), <span style="font-family: Arial, Helvetica, sans-serif;">o2 = new Object();</span>

@Overridepublic void run() {System.out.println("flag=" + flag);if (flag == 1) {synchronized (o1) {try {Thread.sleep(500);} catch (Exception e) {e.printStackTrace();}synchronized (o2) {System.out.println("1");}}}if (flag == 0) {synchronized (o2) {try {Thread.sleep(500);} catch (Exception e) {e.printStackTrace();}synchronized (o1) {System.out.println("0");}}}}public static void main(String[] args) {DeadLock td1 = new DeadLock();DeadLock td2 = new DeadLock();td1.flag = 1;td2.flag = 0;new Thread(td1).start();new Thread(td2).start();}}

当类的对象flag=1时（T1），先锁定O1,睡眠500毫秒，然后锁定O2。而T1在睡眠的时候另一个flag=0的对象（T2）线程启动，先锁定O2,睡眠500毫秒，等待T1释放O1， T1睡眠结束后需要锁定O2才能继续执行，而此时O2已被T2锁定，T2睡眠结束后需要锁定O1才能继续执行，而此时O1已被T1锁定。T1、T2相互等待，都需要对方锁定的资源才能继续执行，从而死锁。