【Java】多线程之线程可见性synchronized

Z时代
2024-01-10
分类：技术分享

synchronized的规定

线程解锁前,必须把共享变量刷新到主内存

线程加锁前将清空工作内存共享变量的值,需要从主存中获取共享变量的值。

synchronized线程可见性安全案例

package com.keytech.task;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class SynchronizedTestOne {
public static void main(String[] args) {
ExecutorService executorService = Executors.newCachedThreadPool();
Rumenzz r=new Rumenzz();
//线程1
executorService.execute(()->{
r.setAge(200);
});
//线程2
executorService.execute(()->{
System.out.println(r.getAge());
});
executorService.shutdown();
}
}
class Rumenzz{
private Integer age=0;
public synchronized Integer getAge() {
return age;
}
public synchronized void setAge(Integer age) {
this.age = age;
}}

package com.keytech.task;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* @className: SynchronizedTestOne
* @description: TODO 类描述
* @author: mac
* @date: 2021/1/1
**/
public class SynchronizedTestOne {
public static void main(String[] args) {
ExecutorService executorService = Executors.newCachedThreadPool();
Rumenzz r=new Rumenzz();
CountDownLatch c=new CountDownLatch(1);
executorService.execute(()->{
try {
c.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(r.getAge());
});
executorService.execute(()->{
try {
Thread.sleep(5000);
c.countDown();
} catch (InterruptedException e) {
e.printStackTrace();
}
r.setAge(200);
});
//关闭线程池
executorService.shutdown();
}
}
class Rumenzz{
private Integer age=0;
public synchronized Integer getAge() {
return age;
}
public synchronized void setAge(Integer age) {
this.age = age;
}}