既然有关监视器monitor的概念比较难，大家怎么解释的都有。首先我给出一下java的官方文档，也是最权威的解释：
Synchronizationis built around an internal entity known as the intrinsic lock ormonitor lock. (The API specification often refers to this entity simplyas a “monitor.”)，Every object has an intrinsic lock associated with it.By convention, a thread that needs exclusive and consistent access toan object’s fields has to acquire the object’s intrinsic lock beforeaccessing them, and then release the intrinsic lock when it’s done withthem.
源自：http://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html
根据官方文档，我来说说我的看法。马克-to-win： synchronized工作机制是这样的：Java中每个对象都有一把锁与之相关联，锁控制着对象的synchronized代码。一个要执行对象的synchronized代码的线程必须先获得那个对象的锁。有点儿监控（monitor）的感觉吗？
synchronized关键字使用方式有两种：synchronized方法和synchronized块。以下会给出例子：
例1.9.3-本章源码class A {
public synchronized void f1() {
for (int i = 0; i < 3; i++) {
try {
Thread.sleep(1000);
} catch (Exception e) {
}
System.out.println(“i = ” + i);
}
}
}
class MyThread extends Thread {
A a;
public MyThread(A a) {
this.a = a;
}
public void run() {
a.f1();
}
}
public class TestMark_to_win {
public static void main(String[] args) {
A a = new A();。。。。。。。。。。。。。。。。。
