Java多线程之多线程工程代码编写思维方式

Java之多线程的工程代码编写思维方式

---

题目：三个售票员卖出30张票，用线程模拟。

---

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并发编程：Lock

---

多线程技巧口诀：

1. 线程 操作 资源类
2. 高内聚 低耦合

---

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：

---

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：

---

带着技巧口诀去一边看一边理解，很重要！