多线程之：死锁
死锁指两个或者多个线程持有锁的同时并等待对方持有的锁，导致无限期等待的情况，通常发生于以不同顺序请求同一组锁。
两个线程以不同顺序获取一组锁会导致死锁，如：
1 public class DeadLockTest { 2 3 public static class LockGroup{ 4 private Object objA=new Object(); 5 private Object objB=new Object(); 6 public Object getObjA() { 7 return objA; 8 } 9 public Object getObjB() { 10 return objB; 11 } 12 13 } 14 15 public static void main(String[] args) throws Exception { 16 final LockGroup group=new LockGroup(); 17 Thread threadA=new Thread(new Runnable() { 18 public void run() { 19 synchronized (group.getObjA()) { 20 System.out.println("try to get lockb......"); 21 synchronized (group.getObjB()) { 22 System.out.println("get all locks now......"); 23 } 24 } 25 } 26 }); 27 Thread threadB=new Thread(new Runnable() { 28 public void run() { 29 synchronized (group.getObjB()) { 30 System.out.println("try to get locka......"); 31 synchronized (group.getObjA()) { 32 System.out.println("get all locks now......"); 33 } 34 } 35 } 36 }); 37 threadA.start(); 38 threadB.start(); 39 threadA.join(); 40 threadB.join();//将会发生死锁 41 } 42 }
