java多线程细节

1.线程名的占用问题

public class Demo1 extends Thread{
	 private String who;  
	 
	    public void run()  
	    {  
	        System.out.println(who + ":" + this.getName());  
	    }  
	    public Demo1(String who)  
	    {  
	        super();  
	        this.who = who;  
	    }  
	    public Demo1(String who, String name)  
	    {  
	        super(name);  
	        this.who = who;  
	    }  
	    public static void main(String[] args)  
	    {  
	    	Demo1 thread1 = new Demo1 ("thread1", "MyThread1");  
	    	Demo1 thread2 = new Demo1 ("thread2","MyThread2");  
	    	Demo1 thread3 = new Demo1 ("thread3");  
	        thread1.start();  
	        thread2.start();  
	        thread3.start();  
	    }
}

结果：

thread1:MyThread1
thread3:Thread-0
thread2:MyThread2

注：输出结果顺序不固定

public class Demo1 extends Thread{
	 private String who;  
	 
	    public void run()  
	    {  
	        System.out.println(who + ":" + this.getName());  
	    }  
	    public Demo1(String who)  
	    {  
	        super();  
	        this.who = who;  
	    }  
	    public Demo1(String who, String name)  
	    {  
	        super(name);  
	        this.who = who;  
	    }  
	    public static void main(String[] args)  
	    {  
	    	Demo1 thread1 = new Demo1 ("thread1", "MyThread1");  
	    	Demo1 thread2 = new Demo1 ("thread2");  
	    	Demo1 thread3 = new Demo1 ("thread3");  
	        thread2.setName("MyThread2");  
	        thread1.start();  
	        thread2.start();  
	        thread3.start();  
	    }
}

thread2:MyThread2
thread3:Thread-1
thread1:MyThread1

通过比较：创建线程时，如果不设置线程名，系统会自动分配线程名，并占位，通过thread3:Thread-1就可断定thread2占据着Thread-0的位置。

2.Thread类的start方法不能多次调用，如不能调用两次thread1.start()方法。否则会抛出一个IllegalThreadStateException异常

3.如果通过继承Runnable的方式创建线程，很多方法都不能用（如isAlive等）
Runnable接口源码如下：

/**
 * The <code>Runnable</code> interface should be implemented by any
 * class whose instances are intended to be executed by a thread. The
 * class must define a method of no arguments called <code>run</code>.
 * <p>
 * This interface is designed to provide a common protocol for objects that
 * wish to execute code while they are active. For example,
 * <code>Runnable</code> is implemented by class <code>Thread</code>.
 * Being active simply means that a thread has been started and has not
 * yet been stopped.
 * <p>
 * In addition, <code>Runnable</code> provides the means for a class to be
 * active while not subclassing <code>Thread</code>. A class that implements
 * <code>Runnable</code> can run without subclassing <code>Thread</code>
 * by instantiating a <code>Thread</code> instance and passing itself in
 * as the target.  In most cases, the <code>Runnable</code> interface should
 * be used if you are only planning to override the <code>run()</code>
 * method and no other <code>Thread</code> methods.
 * This is important because classes should not be subclassed
 * unless the programmer intends on modifying or enhancing the fundamental
 * behavior of the class.
 *
 * @author  Arthur van Hoff
 * @see     java.lang.Thread
 * @see     java.util.concurrent.Callable
 * @since   JDK1.0
 */
public
interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */
    public abstract void run();
}

问题：如果我需要extends其他类，又要用到isAlive方法怎么办？