public class ThreadDemo{
    public static void main(String[] args) {
        for (int i = 0; i < 5; i++) {
            //創(chuàng)建并啟動由繼承Thread類創(chuàng)建的線程
            new Thread(new MyThread(),"Thread"+i).start();
             //創(chuàng)建并啟動由實現(xiàn)Runnable接口創(chuàng)建的線程
            new Thread(new Runner(),"Thread"+i).start();
        }
    }
}

//繼承Thread類
class MyThread extends Thread{
    //重寫run方法
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"由繼承Thread創(chuàng)建");
    }
}

//實現(xiàn)Runnable接口
class Runner implements Runnable{
    //實現(xiàn)run方法
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"有實現(xiàn)Runnable接口創(chuàng)建");
    }
}

//Thread類繼承了Runnable類
public class Thread implements Runnable {}
//Thread的構(gòu)造函數(shù)調(diào)用了init方法
public Thread(Runnable target) {
        init(null, target, "Thread-" + nextThreadNum(), 0);
}
//init調(diào)用了靜態(tài)方法init
private void init(ThreadGroup g, Runnable target, String name,
                      long stackSize) {
        init(g, target, name, stackSize, null, true);
}
//再看靜態(tài)方法init
private void init(ThreadGroup g, Runnable target, String name,
                  long stackSize, AccessControlContext acc,
                  boolean inheritThreadLocals) {
        ...
        //私有Runnable實例
        this.target = target;
        ...
}
//再看一下Runnable方法
@Override
public void run() {
    if (target != null) {
        target.run();
    }
}