1.用同步:有多个线程同时访问共同的数据时必须使用线程同步。Synchronized
2.锁机制:一个线程访问时访问逻辑(共享的数据)锁定,禁止他线程访问
3.多线程:
Thread t1=new Thread(tt);
Thread t2=new Thread(tt);
这才叫多线程;t1和t2同时运行一个对象tt,共享相同数据。
::共享数据只共享属性,不共享局部变量和方法::
4.死锁:为了防止死锁现象,锁定多个对象时,保持顺序一致!
5.线程sleep中,对象锁不释放;
6.
public class DeadLock extends Thread{ private static Object obj1 = new Object(); private static Object obj2 = new Object(); private int flag = 0; public void run(){ if(flag==1){ synchronized(obj1){ try{Thread.sleep(1000);}catch(InterruptedException e){e.printStackTrace();} synchronized(obj2){ System.out.println("1"); } } } if(flag==2){ synchronized(obj2){//obj1死锁 try{Thread.sleep(1000);}catch(InterruptedException e){e.printStackTrace();} synchronized(obj1){//obj2 System.out.println("2"); } } } } public static void main(String[] args) { DeadLock dl = new DeadLock(); DeadLock dl2 = new DeadLock(); dl.flag=1; dl2.flag=2; dl.start(); dl2.start(); } }