Java中的多线程的理解

最新推荐文章于 2022-05-25 17:33:08 发布

原创最新推荐文章于 2022-05-25 17:33:08 发布 · 416 阅读

0 ·

CC 4.0 BY-SA版权

Java 专栏收录该内容

13 篇文章

订阅专栏

Thread与Runnable的区别：

继承自Thread的线程，彼此之间不共享线程的资源；

实现Runnable的接口，各个线程可以共享线程的资源。

看一个实例：

package com.yxf.threadandRunnable;

public class ThreadAndRunnable {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
        MyThread t1 = new MyThread();
        MyThread t2 = new MyThread();
        MyThread t3 = new MyThread();
        t1.start();
        t2.start();
        t3.start();
        System.out.println("----------------------");
        MyRunnable r1 = new MyRunnable();
        new Thread(r1).start();
        new Thread(r1).start();
        new Thread(r1).start();
	}
}

class MyThread extends Thread{
	private int ticket = 5;

	@Override
    public void run() {
	    // TODO Auto-generated method stub
	    for(int i = 0;i < 100;i++){
	        if(ticket > 0){
	        	System.out.println("Thread " + Thread.currentThread().getId() +"-----Ticket_Thread : " + ticket--);
	        }
	    }
    }
}

class MyRunnable implements Runnable{
	private int ticket = 5;

	@Override
    public void run() {
	    // TODO Auto-generated method stub
	    for(int i = 0;i < 100;i++){
	        if(ticket > 0){
	        	System.out.println("Runnable " + Thread.currentThread().getId() + "-----Ticket_Runnable : " + ticket--);
	        }
	    }
    }
}

输出结果如下：

Thread 8-----Ticket_Thread : 5
Thread 8-----Ticket_Thread : 4
Thread 8-----Ticket_Thread : 3
Thread 8-----Ticket_Thread : 2
Thread 8-----Ticket_Thread : 1
----------------------
Thread 10-----Ticket_Thread : 5
Thread 10-----Ticket_Thread : 4
Thread 10-----Ticket_Thread : 3
Thread 10-----Ticket_Thread : 2
Thread 10-----Ticket_Thread : 1
Thread 9-----Ticket_Thread : 5
Thread 9-----Ticket_Thread : 4
Thread 9-----Ticket_Thread : 3
Thread 9-----Ticket_Thread : 2
Thread 9-----Ticket_Thread : 1
Runnable 11-----Ticket_Runnable : 5
Runnable 11-----Ticket_Runnable : 4
Runnable 11-----Ticket_Runnable : 3
Runnable 11-----Ticket_Runnable : 2
Runnable 12-----Ticket_Runnable : 2
Runnable 11-----Ticket_Runnable : 1

继承自Thread的三个线程，他们独立的占有自己线程内的资源。实现Runnable的三个线程，他们共享了线程内的资源，但是也面临一个问题，资源的不同步。

线程的强制执行：
在线程操作中，可以使用join()方法让一个线程强制运行，线程强制运行期间，其他线程无法运行，必须等待此线程完成后才可以继续运行。

package com.yxf.threaddemos;

class MyRunnable implements Runnable{
	@Override
    public void run() {
	    // TODO Auto-generated method stub
	    for(int i = 0;i < 15;i++){
	    	System.out.println("Thread name: " + Thread.currentThread().getName() + ", id = " + 
	                Thread.currentThread().getId() + ", i = " + i);
	    }
    }
}
public class ThreadDemos1 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
        MyRunnable runnable = new MyRunnable();
        Thread thread = new Thread(runnable,"my_thread");
        thread.start();
        /**
         * 当i的值为0-10时，main和my_thread两个线程同时执行，当i > 10 时，my_thread线程被强制执行，直到执行完毕后才会执行main线程。
         */
        for(int i = 0; i < 15;i++){
        	if(i > 10){
        		try{
        			thread.join();
        		}catch (Exception e){
        			
        		}
        	}
        	System.out.println("Thread name: " + Thread.currentThread().getName() + ", id = " +
        	        Thread.currentThread().getId() + ", i = " + i);
        }
	}
}

Output:
Thread name: main, id = 1, i = 0
Thread name: my_thread, id = 8, i = 0
Thread name: my_thread, id = 8, i = 1
Thread name: my_thread, id = 8, i = 2
Thread name: my_thread, id = 8, i = 3
Thread name: my_thread, id = 8, i = 4
Thread name: my_thread, id = 8, i = 5
Thread name: main, id = 1, i = 1
Thread name: my_thread, id = 8, i = 6
Thread name: main, id = 1, i = 2
Thread name: my_thread, id = 8, i = 7
Thread name: main, id = 1, i = 3
Thread name: my_thread, id = 8, i = 8
Thread name: main, id = 1, i = 4
Thread name: my_thread, id = 8, i = 9
Thread name: main, id = 1, i = 5
Thread name: my_thread, id = 8, i = 10
Thread name: main, id = 1, i = 6
Thread name: my_thread, id = 8, i = 11
Thread name: main, id = 1, i = 7
Thread name: my_thread, id = 8, i = 12
Thread name: main, id = 1, i = 8
Thread name: my_thread, id = 8, i = 13
Thread name: main, id = 1, i = 9
Thread name: my_thread, id = 8, i = 14
Thread name: main, id = 1, i = 10
Thread name: main, id = 1, i = 11
Thread name: main, id = 1, i = 12
Thread name: main, id = 1, i = 13
Thread name: main, id = 1, i = 14

线程的休眠:
在程序中允许一个线程进行暂时的休眠，直接使用Thread.sleep()方法即可实现休眠。

package com.yxf.threaddemos2;

class MyRunnable implements Runnable{
	@Override
    public void run() {
	    // TODO Auto-generated method stub
	    for(int i = 0; i < 5;i++){
	    	try{
	    		Thread.sleep(1000);
	    	}catch (Exception e){
	    		e.printStackTrace();
	    	}
	    	//每隔1s钟会打印一次
	    	System.out.println(Thread.currentThread().getName() + ", i = " + i);
	    }
    }
}
public class ThreadDemos2 {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
        MyRunnable runnable = new MyRunnable();
        new Thread(runnable,"my_thread").start();
	}
}

线程的中断:
当一个线程运行时，另外一个线程可以直接通过interrupt()方法中断其运行状态。

package com.yxf.threaddemos3;

class MyRunnable implements Runnable{
	@Override
    public void run() {
	    // TODO Auto-generated method stub
	    System.out.println("Enter run()");
	    try{
	    	Thread.sleep(10000);
	    	System.out.println("Finish sleep()");
	    }catch (Exception e){
	    	System.out.println("Interrupt sleep()");
	    	return;
	    }
	    System.out.println("Finish run()");
    }
}
public class ThreadInterruptDemos {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
        MyRunnable runnable = new MyRunnable();
        Thread thread = new Thread(runnable,"my_thread");
        thread.start();
        try{
        	Thread.sleep(2000);
        }catch (Exception e){
        	
        }
        //这里将thread线程中断，会执行catch中的代码
        thread.interrupt();
	}
}

Output:

Enter run()
Interrupt sleep()