锁

1、分类：

1. 乐观锁
2. 悲观锁
   A. 共享锁
   B. 排他锁
3. 公平锁，非公平锁

2、悲观排他非公平锁
1) 同步方法

       public Sychronized void show(){
       this.wait(int millisec)
       ....
       this.nodify();/this.notifyAll()
       } 
          锁为当前对象    

2）同步代码块

Sychronized(locker){
locker.wait(int millisec)
locker.nodify();/locker.notifyAll()
}

3、
Lock lock = new ReentrantLock(false);//悲观排他true公平，false不公平
Lock lock = new ReentrantLock();//悲观排他非公平锁
Condition cond = lock.newCondition();
try{
lock.lockInterruptibly();
cond.await(int millisec);
cond.signal();/cond.signalAll();
}catch(…){
…
}finally{
lock.unlock();
}

4、读写锁
ReentrantReadWriteLock rw = new ReentrantReadWriteLock(true);
ReentrantReadWriteLock.ReadLock readLock = rw.readLock();
ReentrantReadWriteLock.WriteLock writeLock = rw.writeLock();