彻底搞懂对象并发访问（七）

总览

• 多线程+对象在方法内部
• 多线程+对象在方法外部
• 多线程+单对象+synchronized
• 多线程+多对象+synchronized
• 多线程+synchronized+static
• 多线程+单对象+synchronized+static
• 多线程+多对象+synchronized+static

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多线程+多对象+synchronized+static（例子）

Service类

public class Service {
    synchronized public static void PrintA() {
        try {
            System.out.println("线程名称为：" + Thread.currentThread().getName() +
                    "在" + System.currentTimeMillis() + "进入printA");
            Thread.sleep(3000);
            System.out.println("线程名称为：" + Thread.currentThread().getName() +
                    "在" + System.currentTimeMillis() + "离开printA");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    synchronized public static void printB() {
        System.out.println("线程名称为：" + Thread.currentThread().getName() +
                "在" + System.currentTimeMillis() + "进入printB");
        System.out.println("线程名称为：" + Thread.currentThread().getName() +
                "在" + System.currentTimeMillis() + "离开printB");
    }
    
}

ThreadA.java

public class ThreadA extends Thread {
    private Service service;
    public ThreadA(Service service) {
        this.service = service;
    }
    @Override
    public void run() {
        //注意这里是对象调用
        service.PrintA();
    }
}

ThreadB.java

public class ThreadB extends Thread {
    private Service service;
    public ThreadB(Service service) {
        this.service = service;
    }
    @Override
    public void run() {
        //注意这里是对象调用
        service.printB();
    }
}

Run.java

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

        //这里使用2个对象
        Service service1 = new Service();
        Service service2 = new Service();

        ThreadA a = new ThreadA(service1);
        a.setName("A");
        a.start();

        ThreadB b = new ThreadB(service2);
        b.setName("B");
        b.start();
    }
}

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运行结果

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总结

• 结果是同步的，就是因为Class锁是对所有对象实例起作用的。