java lock -----锁

1. lock And sychronized

用sychronized修饰的方法或者语句块在代码执行完之后锁自动释放，而用Lock需要我们手动释放锁，所以为了保证锁最终被释放(发生异常情况)，要把互斥区放在try内，释放锁放在finally内。

sychronized demo

synchronized(this) { }

lock

 Lock writeLock = lock.writeLock();  
        writeLock.lock();  
        System.out.println("ReadWriteLockTest to addValue: " + v + "   "  
                + System.currentTimeMillis());  
        try {  
            Thread.sleep(1000);  
        } catch (InterruptedException e) {  
        }  
        try {  
            // 做写的工作  
            this.value += v;  
            this.addtimes++;  
        } finally {  
            // 释放writeLock锁  
            writeLock.unlock();  
        }