【Java学习笔记】线程的两种同步方法

线程的两种同步方法

在Java中实现线程同步可以使用synchronized关键字，共有两种方法：

• 同步代码块
• 同步方法

（在Java中共有四种代码块：普通代码块、构造块、静态块、同步块）

同步块

import java.util.concurrent.ExecutionException;

class MyThread implements Runnable{
    private int ticket = 5;
    public void run() {
        for(int i = 0; i < 20; i++)
        {
            //同步块
            synchronized (this) {
                if(this.ticket > 0) {
                    //休眠1秒
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName()+" 卖票，票数 = "+this.ticket--); 
                }
            }
        }

    }
}

public class TestMain {
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        MyThread mt = new MyThread();
        Thread t1 = new Thread(mt,"线程A");
        Thread t2 = new Thread(mt,"线程B");
        Thread t3 = new Thread(mt,"线程C");
        t1.start();
        t2.start();
        t3.start();
    }
}

同步方法

package testThread;

import java.util.concurrent.ExecutionException;

class MyThread implements Runnable{
    private int ticket = 5;
    public void run() {
        for(int i = 0; i < 20; i++)
        {
            this.sale();    //调用同步方法
        }
    }
    //同步方法
    public synchronized void sale() {
        if(this.ticket > 0) {
            //休眠0.1秒
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+" 卖票，票数 = "+this.ticket--); 
        }
    }
}

public class TestMain {
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        MyThread mt = new MyThread();
        Thread t1 = new Thread(mt,"线程A");
        Thread t2 = new Thread(mt,"线程B");
        Thread t3 = new Thread(mt,"线程C");
        t1.start();
        t2.start();
        t3.start();

    }
}

总结

同步操作与异步操作相比，异步操作的执行速度要高于同步操作，但是同步操作时数据的安全性较高，属于安全的线程操作。