鎖物件的改變(菜鳥玩執行緒)
阿新 • • 發佈:2018-12-20
鎖物件的改變
理論
在將任何資料型別作為同步鎖時,需注意的是,是否有多個執行緒同時持有鎖物件,如果同時持有相同的鎖物件,則這些執行緒之間就是同步的;
如果分別獲得鎖物件,這些執行緒之間就是非同步的。
示例
自定義共享變數類
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();
}
}
}
自定義執行緒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();
}
}
自定義執行緒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();
}
}
啟動類
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();
}
}
執行結果及結論
A , BEGIN TIME = 1541735926703
B , BEGIN TIME = 1541735926753
A , END TIME = 1541735928703
B , END TIME = 1541735928753
50毫秒過後執行緒B取得的鎖是"456"
注:只要物件不變,即使物件的屬性改變,執行結果還是同步。