方法一：   
             1.定義線程類實現Runnable接口
             2.Thread myThread = new Thread(target) //target 為Runnable接口類型。
             3.Runnable中只有一個方法：public void run(); //用以定義線程云形體。
             4.使用Runnable接口可以為多個線程提供共享的數據。
             5.在實現Runnable接口的類的run方法定義中可以使用Thread靜態方法：
                                             public static Thread currentThread()//獲取當前線程的引用。

舉例：
         public class TestThread1()  {
            public static void main(String[] args) {
               Runner1 r= new Runner1();
               Thread t = new Thread(r);
               t.start();

               for(int i=0; i<100; i++) {
                  System.out.println("Main Thread:------" + i);
               }
            }
         }
       
         class Runner1 implements Runnable {
            public void run() {
               for (int i=0; i<100; i++) {
                  System.out.println("Runner1 :" + i);
               }
            }
         }

方法二：
             1.可以定義一個Thread的子類并重寫其run方法，如：
                             class MyThread extends Thread {
                                    public void run() {......}
                             }
             2.然后生成該類的對象:
                             MyThread myThread = new MyThread(......)

舉例：
         public class TestThread (
            public static void main(String[] args) {
               Runner1 r = new Runner1();
               r.start();

               for(int i=0; i<100; i++) {
               System.out.println("Main Thread:------" + i);
               }
             }
         )
         

         class Runner1 extends Thread {
            public void run() {
               for (int i=0; i<100; i++) {
               System.out.println("Runner1 :" + i);
            }
         }   

結論：使用第一種方法生成多線程好，因為一個類可以繼承多個接口。而類繼承只能是單繼承。