Reference to proper instance of object volatile variable

Question

How ClassThread can access to variable var from instance of Class1 that created this ClassThread instance?

ClassThread

public class ClassThread implements Runnable {
    @Override
    public void run() {

    }
}

Class1

public class Class1 implements Runnable{

    public volatile String var;

    public Class1() {

    }

    @Override
    public void run() {
        for(int i = 0; i < 5; i++){
            ClassThread ct = new ClassThread();
            Thread t = new Thread(ct);
            t.start();
        }
    }

}

Main

public class Main{
    public static void main(String[] args) {
        for(int i = 0; i < 3; i++){
            Class1 cla = new Class1();
            Thread t = new Thread(cla);
            t.start();
        }
    }
}

Andrew Williamson · Accepted Answer · 2016-02-11 21:45:41Z

1

Take it as an argument in the constructor:

public class ClassThread implements Runnable {
    private volatile String var;

    public ClassThread(String var) {
        this.var = var;
    }

    @Override
    public void run() {

    }
}

And in Class1, pass it in when you construct the ClassThread:

@Override
public void run() {
    for(int i = 0; i < 5; i++){
        ClassThread ct = new ClassThread(var);
        Thread t = new Thread(ct);
        t.start();
    }
}

answered Feb 11, 2016 at 21:45

Andrew Williamson

8,7213 gold badges42 silver badges74 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Michał Piątkowski Over a year ago

And then changes to passed volatile variable will be visible to another threads?

Andrew Williamson Over a year ago

String is immutable, you can't change it. If it were a List, or an Array, then yes, you could change the contents in one thread and then other threads would see the changes. BUT there is potential for race conditions and lost updates, make sure you understand synchronization before changing a variable from multiple threads.

Collectives™ on Stack Overflow

Reference to proper instance of object volatile variable

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related