synchronized关键字的用法

synchronized关键字的用法

1、class monitor

public synchronized static void staticSync()

synchronized (ClassMonitor.class)

2、this monitor

public synchronized void sync()

synchronized (this)

3、monitor

private final Object object= new Object();
synchronized (object)

使用举例

1、类锁

// 类锁 class
public void method_class() {
    try {
        System.out.println(Thread.currentThread().getName() + "  方法开始");
        synchronized (Service.class) {
            extracted();
        }
        System.out.println(Thread.currentThread().getName() + "  方法结束");
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

// 类锁 static syn
public static synchronized void method_syn_static() {
    try {
        System.out.println(Thread.currentThread().getName() + "  方法开始");
        extracted();
        System.out.println(Thread.currentThread().getName() + "  方法结束");
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

2、对象锁

// 对象锁 synchronized
public synchronized void method_syn() {
    try {
        System.out.println(Thread.currentThread().getName() + "  方法开始");
        extracted();
        System.out.println(Thread.currentThread().getName() + "  方法结束");
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

// 对象锁 this
public void method_this() {
    try {
        System.out.println(Thread.currentThread().getName() + "  方法开始");
        synchronized (this) {
            extracted();
        }
        System.out.println(Thread.currentThread().getName() + "  方法结束");
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

3、私有锁

private String lock = new String();

// 私有锁
public void method_pri_lock() {
    try {
        System.out.println(Thread.currentThread().getName() + "  方法开始");
        synchronized (lock) {
            extracted();
        }
        System.out.println(Thread.currentThread().getName() + "  方法结束");
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

// 局部私有锁
public void method_loc_lock() {
    try {
        System.out.println(Thread.currentThread().getName() + "  方法开始");
        String lock = new String();
        synchronized (lock) {
            extracted();
        }
        System.out.println(Thread.currentThread().getName() + "  方法结束");
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

总结：

1、每个类只有一个类锁
2、每个对象对应一个对象锁
3、类锁，对象锁，私有锁彼此之间不会产生竞争
类锁，对象锁，私有锁，竞争分析