Java 多线程线程的线程不安全问题 -- 通过lock解决Java多线程的不安全问题

Java 多线程线程的线程不安全问题 – 创建多线程的两种方式
第一篇文章中，介绍了两种Java 实现多线程的方式（Thread and Runnable）,此时是线程不安全的
本文介绍使用lock对其进行优化。

1.实例化ReentrantLock
2.将同步代码放到try{}finnally{}
3.try 中调用lock.lock，使其变为单线程
4. finally{} 中放置解锁方法: lock.unlock

举例：

import java.util.concurrent.locks.ReentrantLock;


class window7 extends Thread {
    // 1. 实例化ReentrantLock
    ReentrantLock lock = new ReentrantLock();
    private static int ticket = 100;
    @Override
    public void run() {
        while (true) {
            try{
                // 2.在try中调用lock.lock
                lock.lock();
                if (ticket > 0) {
                    try { // 睡眠，让代码有更大机会异常
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    System.out.println(Thread.currentThread().getName() + ":卖票，票号为：" + ticket);
                    ticket--;
                } else {
                    break;
                }
            }finally {
                lock.unlock();
            }
        }
    }
}

public class window7Test {
    public static void main(String[] args) {

        // window1Test win = new window1Test();
        window7 w1 = new window7();
        window7 w2 = new window7();
        window7 w3 = new window7();

        w1.setName("窗口一");
        w2.setName("窗口二");
        w3.setName("窗口三");

        w1.start();
        w2.start();
        w3.start();

    }
}

举例：

import java.util.concurrent.locks.ReentrantLock;


class window8 implements Runnable{


    private int ticket = 100;
    // 1. 实例化ReentrantLock,继承方式需加参数
    ReentrantLock lock = new ReentrantLock(true);
    @Override
    public void run() {
        while (true) {
            try {
                // 2.在try中调用lock.lock
                lock.lock();
                if (ticket > 0) {
                    try { // 睡眠，让代码有更大机会异常
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    System.out.println(Thread.currentThread().getName() + ":卖票，票号为：" + ticket);
                    ticket--;
                } else {
                    break;
                }
            } finally {
                lock.unlock();
            }
        }
    }
}

public class window8Test {
    public static void main(String[] args) {
        //window2Test window = new window2Test();

        window8 win = new window8();

        Thread t1 = new Thread(win);
        Thread t2 = new Thread(win);
        Thread t3 = new Thread(win);

        t1.setName("窗口1");
        t2.setName("窗口2");
        t3.setName("窗口3");

        t1.start();
        t2.start();
        t3.start();
    }
}

本文总结了通过 lock 解决 （Thread and Runnable ）的线程不安全问题。并给出实例代码。