所謂多執行緒，就是計算機同時做幾件事，對外表現的是同時完成。

實現方法

在 JAVA 中就非常比較簡單的了，只需要將新建的類實現 runable 方法，在類中的 run 方法中寫自己要完成的事情。

一個例子

package com.mingsoft;

import java.text.SimpleDateFormat;
import java.util.Date;

public class TestThread3 {
    public static void main(String args[]) {
        Counter c1 = new Counter(1
 
);
        Thread t1 = new Thread(c1);
        Thread t2 = new Thread(c1);
        Thread t3 = new Thread(c1);

        Counter c2 = new Counter(2);
        Thread t4 = new Thread(c2);
        Thread t5 = new Thread(c2);
        Thread t6 = new Thread(c2);

        TimeDisplay timer = new TimeDisplay();
        Thread t7 = new
 
 Thread(timer);
        t1.start();
        //t2.start();
        //t3.start();
        t4.start();
        //t5.start();
        //t6.start();*/
        t7.start();
    }

}

class Counter implements Runnable{
    int id;
    public Counter(int id ) {
        // TODO Auto-generated constructor stub
        this
 
.id = id;
    }
    public void run() {
        int i = 0;
        while (i++ <= 10) {
            System.out.println("ID: " + id + " No. " + i);
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                // TODO: handle exception
            }
        }
    }
}


class TimeDisplay implements Runnable{
    public void run() {
        int i = 0;
        while (i++ <=3) {
            System.out.println(
                    new SimpleDateFormat().format(new Date()));
            try {
                Thread.sleep(40);
            } catch (InterruptedException e) {
                // TODO: handle exception
            }
        }
    }
}

就實現了多執行緒問題