Java中Runnable和Thread的区别

时间:2022-12-11 17:35:44

概述

Runnable 是接口。

Thread 是类,且实现了Runnable接口。

Thread部分源码

public class Thread
    implements Runnable
{
    private static class Caches
    {
 
        static final ConcurrentMap subclassAudits = new ConcurrentHashMap();
        static final ReferenceQueue subclassAuditsQueue = new ReferenceQueue();

在使用Runnable定义的子类中没有start()方法,只有Thread类中才有。

 

1 public interface Runnable
2 {
3  
4     public abstract void run();
5 }

Thread类,有一个构造方法:public Thread(Runnable targer)

 

 1     public Thread(Runnable runnable)
 2     {
 3         daemon = false;
 4         stillborn = false;
 5         threadLocals = null;
 6         inheritableThreadLocals = null;
 7         threadStatus = 0;
 8         blockerLock = new Object();
 9         init(null, runnable, (new StringBuilder()).append("Thread-").append(nextThreadNum()).toString(), 0L);
10     }

此构造方法接受Runnable的子类实例,也就是说可以通过Thread类来启动Runnable实现的多线程。

使用情况

在程序开发中只要是多线程肯定永远以实现Runnable接口为主。

实现Runnable接口相比继承Thread类有如下好处:
1、避免继承的局限,一个类可以继承多个接口。
2、适合于资源的共享。

实例

以卖票为例,总共只有10张动车票了,全国3个窗口在卖。

 

 

继承Thread类的方法

 1 package multithreading;
 2  
 3 public class MyThreadWithExtends extends Thread {
 4  
 5     private int tickets = 10;
 6  
 7     @Override
 8     public void run() {
 9  
10         for (int i = 0; i <= 100; i++) {
11             if(tickets>0){
12                 System.out.println(Thread.currentThread().getName()+"--卖出票:" + tickets--);
13             }
14         }
15     }
16     
17     
18     public static void main(String[] args) {
19         MyThreadWithExtends thread1 = new MyThreadWithExtends();
20         MyThreadWithExtends thread2 = new MyThreadWithExtends();
21         MyThreadWithExtends thread3 = new MyThreadWithExtends();
22  
23         thread1.start();
24         thread2.start();
25         thread3.start();
26         
27         //每个线程都独立,不共享资源,每个线程都卖出了10张票,总共卖出了30张。如果真卖票,就有问题了。
28     }
29  
30 }

运行结果:

Thread-0--卖出票:10

Thread-2--卖出票:10

Thread-1--卖出票:10

Thread-2--卖出票:9

Thread-0--卖出票:9

Thread-2--卖出票:8

Thread-1--卖出票:9

Thread-2--卖出票:7

Thread-0--卖出票:8

Thread-2--卖出票:6

Thread-2--卖出票:5

Thread-2--卖出票:4

Thread-1--卖出票:8

Thread-2--卖出票:3

Thread-0--卖出票:7

Thread-2--卖出票:2

Thread-2--卖出票:1

Thread-1--卖出票:7

Thread-0--卖出票:6

Thread-1--卖出票:6

Thread-0--卖出票:5

Thread-0--卖出票:4

Thread-1--卖出票:5

Thread-0--卖出票:3

Thread-1--卖出票:4

Thread-1--卖出票:3

Thread-1--卖出票:2

Thread-0--卖出票:2

Thread-1--卖出票:1

Thread-0--卖出票:1

每个线程都独立,不共享资源,每个线程都卖出了10张票,总共卖出了30张。如果真卖票,就有问题了。

实现Runnable接口方式

 1 package multithreading;
 2  
 3 public class MyThreadWithImplements implements Runnable {
 4  
 5     private int tickets = 10;
 6  
 7     @Override
 8     public void run() {
 9  
10         for (int i = 0; i <= 100; i++) {
11             if(tickets>0){
12                 System.out.println(Thread.currentThread().getName()+"--卖出票:" + tickets--);
13             }
14         }
15     }
16     
17     
18     public static void main(String[] args) {
19         MyThreadWithImplements myRunnable = new MyThreadWithImplements();
20         Thread thread1 = new Thread(myRunnable, "窗口一");
21         Thread thread2 = new Thread(myRunnable, "窗口二");
22         Thread thread3 = new Thread(myRunnable, "窗口三");
23  
24         thread1.start();
25         thread2.start();
26         thread3.start();
27     }
28  
29 }

运行结果:

 

窗口二--卖出票:10
窗口三--卖出票:9
窗口一--卖出票:8
窗口三--卖出票:6
窗口三--卖出票:4
窗口三--卖出票:3
窗口三--卖出票:2
窗口三--卖出票:1
窗口二--卖出票:7
窗口一--卖出票:5

 

每个线程共享了对象myRunnable的资源,卖出的总票数是对的,但是顺序是乱的,怎么办?

见:同步关键词synchronized