public class MyThread extends Thread {

    public MyThread() {
        System.out.println(Thread.currentThread().getName()
                + " :: this.isAlive() :: " + this.isAlive());
        System.out.println(Thread.currentThread().getName()
                + " :: Thread.currentThread().isAlive() :: "
                + Thread.currentThread().isAlive());
    }

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()
                + " :: this.isAlive() :: " + this.isAlive());
        System.out.println(Thread.currentThread().getName()
                + " :: Thread.currentThread().isAlive() :: "
                + Thread.currentThread().isAlive());
    }

    /**
     * 在调用thread1.start()方法后，thread1的this.isAlive()==true；
     * 而将new Mythread()对象以参数的形势传入new Thread()构造器后，
     * 再调用thread2.start()方法后，thread2的this.isAlive()==false.
     */
    public static void main(String[] args) {
        MyThread thread1 = new MyThread();
        thread1.start();
        Thread thread2 = new Thread(new MyThread());
        thread2.start();
    }
}

• 当直接调用线程对象的start()方法时，在run()方法中调用this.isAlive()为true；
• 当将线程对象以构造函数参数的方式传递给Thread对象，调用该Thread对象的start()方法时，在run()方法中调用this.isAlive()为false；
• 相比较之下run()方法中的Thread.currentThread().isAlive()一直为true；
  
  运行结果

Java多线程编程核心技术 高洪岩著