线程相关理解

朱雀 2024-03-16 22:38 33阅读 0赞

## 一.相关概念 ##

> 进程：正在运行的应用程序（官方概念：一个正在运行的程序拥有该程序运行的所有资源，包括资源的分配和任务调度。）  
> 线程：进程中的执行单元（作用：提升应用程序的执行效率）（官方概念：在进程中负责具体代码的执行，一个进程至少有一个线程。）  
> 并行：两个应用程序跑在两个不同的核上同时进行  
> 并发：交叉交替执行的任务

## 二实现线程的方法 ##

方法一：  
创建一个类，继承Thread类，重写run方法，再调用start方法（单继承，有限制，有开辟线程的能力，资源共享方面不是很方便）

代码演示一：  
**MyThread类**

public class MyThread extends Thread{
        
        @Override
        public void run(){
        
            run1();
        }
        
        public void run1(){
        
            for(int i = 0; i < 100; i++){
        
                System.out.println("MyThread---->" + i);
            }
        }
    }

**ThreadDemo类**

package ThreadDemo;
     
    public class ThreadDemo {
        
        public static void main(String [] args){
        
            MyThread myThread = new MyThread();
            myThread.start();
            for(int i = 0; i< 100; i++){
        
                System.out.println("main---->" + i);
            }
        }
    }

运行结果：

package ThreadDemo;

public class ThreadDemo \{  
public static void main(String \[\] args)\{  
MyThread myThread = new MyThread();  
myThread.start();  
for(int i = 0; i< 100; i++)\{  
System.out.println(“main---->” + i);  
\}  
\}  
\}  
运行结果：  
![在这里插入图片描述][261703dc87664a749109e071531af0cb.png]  
代码演示二：  
**TicketsThread类**

public class TicketsThread extends Thread{
        
        private int num;
        public  TicketsThread(){
        }
        public TicketsThread(int num){
        
            this.num = num;
        }
     
        public void setNum(int num){
        
            this.num = num;
        }
        public int getNum(){
        
            return this.num;
        }
     
        @Override
        public void run(){
        
            while(this.num > 0){
        
                sale();
            }
        }
        public void sale(){
        
            this.num = --num;
            System.out.println(Thread.currentThread().getName() + "Thread--->剩余票数：" + this.num);
            this.setNum(num);
        }
    }

**ThreadDemo类**

public class ThreadDemo {
        
        public static void main(String [] args){
        
            TicketsThread ticketsThread = new TicketsThread(1000);
            ticketsThread.start();
            while(ticketsThread.getNum() > 0){
        
                ticketsThread.sale();
            }
        }
    }

运行结果：  
![在这里插入图片描述][bb59c7f916c64530aed08119d1ac2886.png]  
方法二：  
实现Runnable接口，重新run方法。在传给Thread构造器，调用时调用Thread的start方法。（多实现，更灵活，推荐使用，没有开辟线程的能力，要将创建的对象交给指定线程来运行）。

代码演示：  
**RunnableTest类**

public class RunnableTest implements Runnable{
        
        @Override
        public void run(){
        
            for(int i = 0; i < 100; i++){
        
                System.out.println("分支线程" + i);
            }
        }
    }

**Test类**

public class Test {
        
        public static void main(String [] args){
        
            RunnableTest1 r1 = new RunnableTest1();
            Thread t1 = new Thread(r1);
            t1.start();
            RunnableTest1 r2 = new RunnableTest1(){
        
                @Override
                public void run(){
        
                    for(int i = 0; i< 100;i++){
        
                        System.out.println("main线程" + i);
                    }
                }
            }; // 内部类
            Thread t2 = new Thread(r2);
            t2.start();
        }
    }

运行结果：  
![在这里插入图片描述][34f5308855a7433fa5aa6c11475211dd.png]

## 三、多线程实现售票 ##

**Tickets类**

public class Tickets extends Thread{
        
     
        private int num;
     
        public Tickets(){
        }
     
        public Tickets(int num){
        
            this.num = num;
        }
     
        public int getNum() {
        
            return num;
        }
     
        public void setNum(int num) {
        
            this.num = num;
        }
    }

**Operate类**

public class Operate {
        
     
        private Tickets tickets;
     
        public Operate(Tickets tickets){
        
            this.tickets = tickets;
        }
     
        public void sale(){
        
            synchronized (this){
         //  synchronized   锁    同步    只能锁对象
                try{
        
                    Thread.sleep(100);
                } catch (InterruptedException e){
        
                    e.printStackTrace();
                }
            }
            if(tickets.getNum() > 0){
        
                int num = tickets.getNum();
                System.out.println(Thread.currentThread().getName() + " 正在售卖 " + tickets.getNum() + " 张票，剩余 " + (tickets.getNum() - 1));
                num--;
                tickets.setNum(num);
            }
        }
    }

**Test类**

public class Test {
        
        public static void main(String [] args){
        
            Tickets tickets = new Tickets(100);
            Operate operate = new Operate(tickets);
     
            new Thread(() -> {
        
                while(tickets.getNum() > 0) operate.sale();
            },"窗口一").start();
     
            new Thread(() -> {
        
                while(tickets.getNum() > 0) operate.sale();
            },"窗口二").start();
     
            new Thread(() -> {
        
                while(tickets.getNum() > 0) operate.sale();
            },"窗口三").start();
        }
    }

运行结果：  
![在这里插入图片描述][b3acb16e16f948968f046da17251cdd4.png]

[261703dc87664a749109e071531af0cb.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/56a894afec304e928a420e4c6f4fabb6.png
[bb59c7f916c64530aed08119d1ac2886.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/4bd28b0f028041539ede808bbd8f193c.png
[34f5308855a7433fa5aa6c11475211dd.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/c4da86aaf0e34c73b2c6fc96dabd96db.png
[b3acb16e16f948968f046da17251cdd4.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/b47c3ca0caaa4506875daac813de2106.png