线程死锁

为了避免多线程访问共享资源是会加上同步锁,避免安全问题,但是加了同步锁可能导致死锁.

发生死锁的原因:

1, 同步代码块内嵌套了同步代码快

2, 并且他们的锁对象不一样

例如:

class DeadLocker implements Runnable{
	private boolean mFlag;
	DeadLocker(boolean flag){
		mFlag = flag;
	}
	
	public void run(){
		if(mFlag){
				synchronized(LockerObjects.obj1){
					System.out.println(Thread.currentThread().getName() + ", run to A");
					synchronized(LockerObjects.obj2){
						System.out.println(Thread.currentThread().getName() + ", run to A");
					}
				}
		}
		else{
				synchronized(LockerObjects.obj2){
					System.out.println(Thread.currentThread().getName() + ", run to C");
					synchronized(LockerObjects.obj1){
						System.out.println(Thread.currentThread().getName() + ", run to D");
					}
				}
		}
	}
}

class LockerObjects{
	public static final Object obj1 = new Object();
	public static final Object obj2 = new Object();
}