解决线程不安全的方式（Java）

Posted 2020-11-28 孙小龙

一、同步代码块

package com.synchronized1;

// 买票示例
// 使用同步代码块解决线程安全问题
public class TicketRunnableImp implements Runnable {
    private int ticket = 100;
    Object o=new Object();
    @Override
    public void run() {
        while (true) {
            synchronized (o){
                if (ticket > 0) {
                    System.out.println(Thread.currentThread().getName() + "-->正在售第"+ticket+"张票！");
                    ticket--;
                }
            }
        }
    }
}

二、同步方法

package com.synchronized2;

// 买票示例
// 使用同步方法解决线程安全问题
public class TicketRunnableImp implements Runnable {
    private int ticket = 100;
    Object o = new Object();

    @Override
    public void run() {
        while (true) {
            func();
        }
    }
    // 同步方法的锁对象是调用者对象（Runnable对象）
    public synchronized void func(){
        if (ticket > 0) {
            System.out.println(Thread.currentThread().getName() + "-->正在售第" + ticket + "张票！");
            ticket--;
        }
    }
}

三、静态方法

package com.staticSyn;

// 买票示例
// 使用同步方法解决线程安全问题
public class TicketRunnableImp implements Runnable {
    private static int ticket = 100;
    Object o = new Object();

    @Override
    public void run() {
        while (true) {
            func();
        }
    }
    // 静态方法的锁对象是本类的class属性
    public synchronized static void func(){
        if (ticket > 0) {
            System.out.println(Thread.currentThread().getName() + "-->正在售第" + ticket + "张票！");
            ticket--;
        }
    }
}

四、Lock锁

方式一

package com.lock1;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

// 买票示例
// 使用同步代码块解决线程安全问题
public class TicketRunnableImp implements Runnable {
    private int ticket = 100;
    Object o = new Object();
    Lock lock=new ReentrantLock();
    @Override
    public void run() {
        while (true) {
            lock.lock();
            if (ticket > 0) {
                System.out.println(Thread.currentThread().getName() + "-->正在售第" + ticket + "张票！");
                ticket--;
            }
            lock.unlock();
        }
    }
}

方式二

package com.lock2;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

// 买票示例
// 使用同步代码块解决线程安全问题
public class TicketRunnableImp implements Runnable {
    private int ticket = 100;
    Object o = new Object();
    Lock lock = new ReentrantLock();

    @Override
    public void run() {
        while (true) {
            lock.lock();
            try {
                if (ticket > 0) {
                    System.out.println(Thread.currentThread().getName() + "-->正在售第" + ticket + "张票！");
                    ticket--;
                }
            } catch (Exception e) {
                System.out.println(e);
            } finally {
                lock.unlock();
            }
        }
    }
}

五、上述几种方式的测试类

package com.lock2;

public class DemoTicket {
    public static void main(String[] args) {
        TicketRunnableImp t=new TicketRunnableImp();
        Thread t1=new Thread(t);
        Thread t2=new Thread(t);
        Thread t3=new Thread(t);
        t1.start();
        t2.start();
        t3.start();
    }
}