java线程同步方法，方法块差别

先说同步方法。它究竟是锁定的当前对象，还是当前类

代码块1

package com.ssss;

public class Thread1 implements Runnable {  
	//public static Object  o=new Object();

    public void run() {
    	pt();
    }
    
    public synchronized void pt(){
    	int a=0;
        //synchronized(o) {  
             for (int i = 0; i < 5; i++) {
           	  a++;
           	  try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
                  System.out.println(Thread.currentThread().getName() + " synchronized loop " + i + "++++" + a);  
             }  
        //}  
    }
    
    
    public static void main(String[] args) {  
         Thread1 t1 = new Thread1();  
         Thread1 t2 = new Thread1();  

         Thread ta = new Thread(t1, "A");  
         Thread tb = new Thread(t2, "B");  
         ta.start();  
         tb.start();  
    } 
}

打印出来的结果为

由此可见是当前对象，而A和B是两个不同的对象。所以打印序列就是混乱的

代码块2

看同步块

package com.ssss;

public class Thread1 implements Runnable {  
	public static Object  o=new Object();

    public void run() {
    	pt();
    }
    
    public void pt(){
    	int a=0;
        synchronized(o) {  
             for (int i = 0; i < 5; i++) {
           	  a++;
           	  try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
                  System.out.println(Thread.currentThread().getName() + " synchronized loop " + i + "++++" + a);  
             }  
        }  
    }
    
    
    public static void main(String[] args) {  
         Thread1 t1 = new Thread1();  
         Thread1 t2 = new Thread1();  

         Thread ta = new Thread(t1, "A");  
         Thread tb = new Thread(t2, "B");  
         ta.start();  
         tb.start();  
    } 
}

看打印序列

说明同步块能够锁定不论什么对象

就是说同步方法是锁定当前对象，同步方法块是能够锁定不论什么对象