Java多线程之多线程工程代码编写思维方式

冷不防 2022-01-31 22:49 218阅读 0赞

# Java之多线程的工程代码编写思维方式 #

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#### 题目：三个售票员卖出30张票，用线程模拟。 ####

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##### 前言： #####

*  本文涉及`synchronized`、`Lock`和`拉姆达表达式(Lambda Expressions)`，前两知识点推荐看这两篇写的很好的详解文章。
 *  [Java并发编程：synchronized][Java_synchronized]
 *  [Java并发编程：Lock][Java_Lock]

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#### 多线程技巧口诀： ####

1.  线程 操作 资源类
2.  高内聚 低耦合

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**未优化的代码：**

import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    class Ticket {
        
        private int number = 30; //模拟票数
        private int num = 1;
    
        public synchronized void sale() {
        
            if (number > 0) {
        
                System.out.println(Thread.currentThread().getName() + "\t卖出第：" + (num++)+ "张，还剩下：" + --number);
            }
        }
    }
    
    
    public class ThreadDemo4 {
        
        public static void main(String[] args) {
        
    
            Ticket ticket = new Ticket();
    
            new Thread(new Runnable() {
        
                @Override
                public void run() {
        
                    for (int i = 1; i < 40; i++) {
        
                        ticket.sale();
                    }
                }
            }, "A").start();
    
            new Thread(new Runnable() {
        
                @Override
                public void run() {
        
                    for (int i = 1; i < 40; i++) {
        
                        ticket.sale();
                    }
                }
            }, "B").start();
    
            new Thread(new Runnable() {
        
                @Override
                public void run() {
        
                    for (int i = 1; i < 40; i++) {
        
                        ticket.sale();
                    }
                }
            }, "C").start();
        }
    }

**结果部分截图：**  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTkxMDY5NA_size_16_color_FFFFFF_t_70][]

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**利用`拉姆达表达式(Lambda Expressions)`和`Lock`对代码进行优化。**

import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    class Ticket {
        
        private int number = 30; //模拟票数
        private Lock lock = new ReentrantLock();
        private int num = 1;
    
        public void sale() {
        
            lock.lock();
            try {
        
                if (number > 0) {
        
                    System.out.println(Thread.currentThread().getName() + "\t卖出第：" + (num++) + "张，还剩下：" + --number);
                }
            } catch (Exception e) {
        
                e.printStackTrace();
            } finally {
        
                lock.unlock();
            }
        }
    }
    
    
    public class ThreadDemo1 {
        
        public static void main(String[] args) {
        
    
            Ticket ticket = new Ticket();
    
            new Thread(() -> {
        for (int i = 1; i < 40; i++) {
        ticket.sale();} }, "A").start();
    
            new Thread(() -> {
        for (int i = 1; i < 40; i++) {
        ticket.sale();} }, "B").start();
    
            new Thread(() -> {
        for (int i = 1; i < 40; i++) {
        ticket.sale();} }, "C").start();
        }
    }
    
    ---

**结果部分截图：**  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTkxMDY5NA_size_16_color_FFFFFF_t_70][]

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##### `带着技巧口诀去一边看一边理解，很重要！` #####

[Java_synchronized]: https://www.cnblogs.com/dolphin0520/p/3923737.html
[Java_Lock]: https://www.cnblogs.com/dolphin0520/p/3923167.html
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTkxMDY5NA_size_16_color_FFFFFF_t_70]: /images/20220201/69a304e7f6334f29995b2a7342a5bd67.png