线程的基本用法

实现多线程的方法有3种:
1.继承thread类
  eg : 定义: public class firstThread extends Thread
       调用: firstThread ft = new firstThread();
             ft.start();
2.实现Runnable接口
  eg : 定义: public class MyRunnable implements Runnable
       调用: MyRunnable mr = new MyRunnable();
            Thread tr = new Thread(mr);
   tr.start();
3.运用Timer 和 TimerTask 类实现
  eg :  创建Timer 
           Timer t = new Timer();
        创建TimerTask
           MyTimerTask mtt1 = new MyTimerTask("线程1：");
        启动线程
             t.schedule(mtt1, 0);