Thread和Runnable的区别

1. 实现Runnable接口，可以避免java单继承机制带来的局限；
2. 实现Runnable接口，可以实现多个线程共享同一段代码(数据)；
   ex：

public class ThreadTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        
        MyThread thread1 = new MyThread();
        MyThread thread2 = new MyThread();
        MyThread thread3 = new MyThread();
        thread1.start();
        thread2.start();
        thread3.start();
        
        MyRunnable runnable1 = new MyRunnable("r1");
        
        new Thread(runnable1).run();
        new Thread(runnable1).run();
        new Thread(runnable1).run();
        
    }

}

class MyThread extends Thread
{
    int things = 5;
    @Override
    public void run() {
        while(things > 0)
        {
            System.out.println(currentThread().getName() + " things:" + things);
            things--;
        }
    }
}

class MyRunnable implements Runnable
{
    String name;
    
    public MyRunnable(String name)
    {
        this.name = name;
    }
    
    int things = 5;
    @Override
    public void run() {
        while(things > 0)
        {
            things--;
            System.out.println(name + " things:" + things);
        }
        
    }
}

运行结果：

Thread-2 things:5
r1 things:4
r1 things:3
Thread-1 things:5
Thread-1 things:4
Thread-1 things:3
r1 things:2
Thread-2 things:4
Thread-2 things:3
Thread-2 things:2
Thread-2 things:1
r1 things:1
Thread-1 things:2
r1 things:0
Thread-1 things:1
Thread-0 things:5
Thread-0 things:4
Thread-0 things:3
Thread-0 things:2
Thread-0 things:1

注解：多个Thread可以同时加载一个Runnable，当各自Thread获得CPU时间片的时候开始运行runnable，runnable里面的资源是被共享的。

3. 线程池只能放入实现Runable或Callable类线程，不能直接放入继承Thread的类。