1. 實(shí)現(xiàn)Runnable接口，可以避免java單繼承機(jī)制帶來(lái)的局限；
2. 實(shí)現(xiàn)Runnable接口，可以實(shí)現(xiàn)多個(gè)線程共享同一段代碼(數(shù)據(jù))；
   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);
        }
        
    }
}

運(yùn)行結(jié)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：多個(gè)Thread可以同時(shí)加載一個(gè)Runnable，當(dāng)各自Thread獲得CPU時(shí)間片的時(shí)候開始運(yùn)行runnable，runnable里面的資源是被共享的。

3. 線程池只能放入實(shí)現(xiàn)Runable或Callable類線程，不能直接放入繼承Thread的類。