锁对象的改变（菜鸟玩线程）

ゝ一世哀愁。 2024-02-19 13:13 44阅读 0赞

## 锁对象的改变 ##

### 理论 ###

`在将任何数据类型作为同步锁时，需注意的是，是否有多个线程同时持有锁对象，如果同时持有相同的锁对象，则这些线程之间就是同步的；`

`如果分别获得锁对象，这些线程之间就是异步的。`

### 示例 ###

#### 自定义共享变量类 ####

package com.chapter02.thread2_2_16;
    public class MyService {
        
        private String lock = "123";
        public void testMethod() {
        
            try {
        
                synchronized (lock) {
        
                    System.out.println(Thread.currentThread().getName() + " , BEGIN TIME = " + System.currentTimeMillis());
                    lock = "456";
                    Thread.sleep(2000);
                    System.out.println(Thread.currentThread().getName() + " , END TIME = " + System.currentTimeMillis());
                }
            } catch (Exception ex) {
        
                ex.printStackTrace();
            }
        }
    }

#### 自定义线程1 ####

package com.chapter02.thread2_2_16;
    public class ThreadA extends Thread {
        
        private MyService service;
    
        public ThreadA(MyService service) {
        
            this.service = service;
        }
    
        @Override
        public void run() {
        
            super.run();
            service.testMethod();
        }
    }

#### 自定义线程2 ####

package com.chapter02.thread2_2_16;
    public class ThreadB extends Thread {
        
        private MyService service;
    
        public ThreadB(MyService service) {
        
            this.service = service;
        }
    
        @Override
        public void run() {
        
            super.run();
            service.testMethod();
        }
    }

#### 启动类 ####

package com.chapter02.thread2_2_16;
    public class Main1 {
        
        public static void main(String[] args) throws InterruptedException {
        
            MyService myService = new MyService();
    
            ThreadA a = new ThreadA(myService);
            a.setName("A");
            ThreadB b = new ThreadB(myService);
            b.setName("B");
    
            a.start();
            Thread.sleep(50);
            b.start();
        }
    }

#### 执行结果及结论 ####

A , BEGIN TIME = 1541735926703
    B , BEGIN TIME = 1541735926753
    A , END TIME = 1541735928703
    B , END TIME = 1541735928753

`50毫秒过后线程B取得的锁是"456"`

`注：只要对象不变，即使对象的属性改变，运行结果还是同步。`