Synchronized的两个用法

Synchronized的作用：

能够保证在同一时刻最多只有一个线程执行该段代码，以达到保证并发安全的效果

Synchronized的两个用法：

1）对象锁

包括方法锁（默认锁对象为this当前实例对象）和同步代码块锁（自己指定锁对 象）

2）类锁：

指Synchronized修饰静态的方法或指定锁为Class对象

public class SynchronizedObjectCodeBlock2 implements Runnable {

    static SynchronizedObjectCodeBlock2 intface = new SynchronizedObjectCodeBlock2();
    Object lock1 = new Object();
    Object lock2 = new Object();

    @Override
    public void run() {
        synchronized (lock1) {
            System.out.println("lock1部分。我叫：" + Thread.currentThread().getName());
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "lock1部分运行结束！");
        }

        synchronized (lock2) {
            System.out.println("lock2部分。我叫：" + Thread.currentThread().getName());
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "lock2部分运行结束！");
        }
    }

    public static void main(String[] args) {
        Thread t1 = new Thread(intface);
        Thread t2 = new Thread(intface);
        t1.start();
        t2.start();
        while (t1.isAlive() || t2.isAlive()) {

        }
        System.out.println("finshed");
    }
}

运行结果：

public class SynchronizedObjectMethod3 implements Runnable {

    static SynchronizedObjectMethod3 intface = new SynchronizedObjectMethod3();

    @Override
    public void run() {
        method();
    }

    public static void main(String[] args) {
        Thread t1 = new Thread(intface);
        Thread t2 = new Thread(intface);
        t1.start();
        t2.start();
        while (t1.isAlive() || t2.isAlive()) {

        }
        System.out.println("finshed");
    }

    public synchronized void method() {
        System.out.println("我是对象锁的方法修饰符形式。我叫："+ Thread.currentThread().getName());
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName()+"运行结束");
    }
}

运行结果：

public class SynchronizedClassStatic4 implements Runnable {

    static SynchronizedClassStatic4 intface1 = new SynchronizedClassStatic4();
    static SynchronizedClassStatic4 intface2 = new SynchronizedClassStatic4();

    @Override
    public void run() {
        method();
    }

    public static synchronized void method(){
        System.out.println("我是类锁的第一种形式：static形式。我叫："+ Thread.currentThread().getName());
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName()+"运行结束");
    }

    public static void main(String[] args) {
        Thread t1 = new Thread(intface1);
        Thread t2 = new Thread(intface2);
        t1.start();
        t2.start();
        while (t1.isAlive() || t2.isAlive()) {

        }
        System.out.println("finshed");
    }
}

运行结果：

public class SynchronizedClassClass5 implements Runnable {

    static SynchronizedClassClass5 intface1 = new SynchronizedClassClass5();
    static SynchronizedClassClass5 intface2 = new SynchronizedClassClass5();

    @Override
    public void run() {
        method();
    }

    public void method(){
        synchronized (SynchronizedClassClass5.class){
            System.out.println("我是类锁的第2种形式：synchronized (*.class)形式。我叫："+ Thread.currentThread().getName());
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+"运行结束");
        }
    }

    public static void main(String[] args) {
        Thread t1 = new Thread(intface1);
        Thread t2 = new Thread(intface2);
        t1.start();
        t2.start();
        while (t1.isAlive() || t2.isAlive()) {

        }
        System.out.println("finshed");
    }
}

运行结果：