使引用变量易变，在Java中也使它的所有字段也易变吗?

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问题描述

我已经读到使引用变量为volatile并不会使其内部字段为volatile.但是我尝试使用下面的示例，其中看起来像volatile性质也适用于类的内部字段.

I have read that making reference variable volatile, does not make its inner fields volatile.But i tried with below example where it looks like volatile nature is applied to inner fields of class as well.

User.java:-//将字段标志"设置为true的用户类.

User.java:-// user class having field "flag" set as true.

public class User {

    private boolean flag=true;

    public boolean isFlag() {
        return flag;
    }

    public void setFlag(boolean flag) {
        this.flag = flag;
    }
}

MyRunnableThread1.java:-

在这里，我将用户"设置为易失性，而不是将其内部字段标志"设置为易失性

here i have made "user" as volatile and not its inner field "flag" as volatile

子线程在"while(this.user.isFlag())"处连续循环.

child thread is continuously in loop at "while(this.user.isFlag())".

public class MyRunnableThread1 implements Runnable {

    private String threadName;
    private  volatile User  user; 

    public MyRunnableThread1(String threadName,User user)
    {
        this.threadName=threadName; 
        this.user=user;
    } 

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    @Override
    public void run() {

        System.out.println("child thread:"+threadName+" started");

        while(this.user.isFlag()) {

        }
        System.out.println("child thread:"+threadName+" finished");
    }
}

ThreadDemo.java:-

在主线程中，我们将"User"对象的字段"flag"的值设置为false终止子线程中的循环

in main thread we sets the value of field "flag" of "User" object as falseto terminate the loop in child thread

public class ThreadDemo {

    public static void main(final String[] arguments) throws InterruptedException {

        System.out.println("main thread started");

        User user=new User(); 
        MyRunnableThread1 myRunnableThread1=new MyRunnableThread1("Thread1",user);
        Thread t=new Thread(myRunnableThread1);
        t.start();

        try {
            Thread.sleep(6000);
        }
        catch(Exception e) {
            System.out.println("exception in sleep:"+e);
        }

        myRunnableThread1.getUser().setFlag(false);

        System.out.println("main thread finished"); 
    }
}

o/p:-

主线程已启动子线程:Thread1已启动主线程完成子线程:线程1完成

main thread startedchild thread:Thread1 startedmain thread finishedchild thread:Thread1 finished

在上面的示例中，我在"MyRunnableThread1.java"类中将"user"变量设置为volatile.用户对象的字段"flag"在实例化时为true.在开始连续执行循环的子线程之后，主线程将用户对象的字段"flag"的值更改为false.但是这里"flag"字段不是volatile，而是"user"引用变量是volatile.但是这里主线程中"flag"字段的值变化仍然反映在子线程中.它的行为就像"flag"字段也是易挥发的.任何人都可以帮助解决上述问题吗?

In above example I have made "user" variable as volatile in "MyRunnableThread1.java" class.User object has field "flag" which is true at time of instantiation.After starting the child thread where it continuously execute the loop , the main thread changes the value of field "flag" of user object to false.But here field "flag" is not volatile instead the "user" reference variable is volatile.But still here the change in value of field "flag" in main thread is reflected in child thread.It behaves as if field "flag" is also volatile.can anyone help with above issue??

volatile

使引用变量易变，在Java中也使它的所有字段也易变吗?

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