是这样的，我想知道synchronized(obj)的用法，然后写了如下的代码，运行结果我如何都搞不清，还请各位指点。
代码1：
public class MyObj
{
private Integer a;
private Double b;
private Integer c;
public void setA()
{
System.out.println(Thread.currentThread().getName() + "抢到锁..setA");
synchronized(c)
{
System.out.println(" " + Thread.currentThread().getName() + " " + this.a + " " + this.b);
this.a = 1;
this.b = 2.0;
try{
Thread.sleep(200);//(int) (Math.random()*2000)
}catch(InterruptedException e) {
e.printStackTrace();
}
System.out.println(" " + Thread.currentThread().getName() + " " + this.a + " " + this.b);
}
}
public void setB()
{
System.out.println(Thread.currentThread().getName() + "抢到锁....setB");
synchronized(c)
{
System.out.println(" " + Thread.currentThread().getName() + " " + this.a + " " + this.b);
this.a = 3;
this.b = 4.0;
try{
Thread.sleep(200);//(int) (Math.random()*2000)
}catch(InterruptedException e) {
e.printStackTrace();
}
System.out.println(" " + Thread.currentThread().getName() + " " + this.a + " " + this.b);
}
}
public MyObj()
{
this.a = -1;
this.b = -1.0;
this.c = 0;
}
}
代码2：
public class Change
{
private MyObj myObj;
public Change(MyObj myObj)
{
this.myObj = myObj;
}
public static void main(String args[])
{
final MyObj myObj = new MyObj();
final Integer a = 1;
Thread thread1 = new Thread(new Runnable(){
public void run()
{
for(int product = 1; product <= 3; ++product)
{
try{
Thread.sleep((int) (Math.random()*200));//(int) (Math.random()*2000)
myObj.setA();
}catch(InterruptedException e)
{
e.printStackTrace();
}
}
}
},"thread1");
Thread thread2 = new Thread(new Runnable(){
public void run()
{
for(int product = 1; product <= 3; ++product)
{
try{
Thread.sleep((int) (Math.random()*200));//(int) (Math.random()*2000)
myObj.setB();
}catch(InterruptedException e)
{
e.printStackTrace();
}
}
}
},"thread2");
thread1.start();
thread2.start();
}
}
输出结果（之一）：
thread2抢到锁....setB
thread2 -1 -1.0
thread1抢到锁..setA
thread2 3 4.0
thread1 3 4.0
thread2抢到锁....setB
thread1 1 2.0
thread2 1 2.0
thread1抢到锁..setA
thread2 3 4.0
thread1 3 4.0
thread2抢到锁....setB
thread1 1 2.0
thread2 1 2.0
thread1抢到锁..setA
thread2 3 4.0
thread1 3 4.0
thread1 1 2.0
** 但是**，如果将
System.out.println(Thread.currentThread().getName() + "抢到锁....setA");
和
System.out.println(Thread.currentThread().getName() + "抢到锁....setB");
放到 synchronized(c) 块里面，那么结果之一：
thread1抢到锁..setA
thread1 -1 -1.0
thread1 1 2.0
thread2抢到锁....setB
thread2 1 2.0
thread2 3 4.0
thread1抢到锁..setA
thread1 3 4.0
thread1 1 2.0
thread2抢到锁....setB
thread2 1 2.0
thread2 3 4.0
thread1抢到锁..setA
thread1 3 4.0
thread1 1 2.0
thread2抢到锁....setB
thread2 1 2.0
thread2 3 4.0
可能 输出有先后，但是 至少 thread1，thread2的输出之间，不会相互干扰。。。
我仔细观察了，上面的结果，虽然相互干扰，但是也不会出错，但是为什么 会这样呢？ 既然 已经进入 thread1了，thread2怎么还能得到锁呢。。如果这样的话，synchronized(obj)还有啥意思啊(obj不一定是this)？ 。实在没搞懂啊。再次麻烦各位帮忙。
总共就1个币，谅解哈。
