abstract class as shared memory on different threads

Question

I have an abstract class which is inherited by classes that run on different threads. do the variables in this abstract class act as shared memory?

public abstract class A
{
   public abstract void foo();

   public boolean bar(){
   {
      List<String> x=new ArrayList();
      x.add("a");
      //some code
   }
}
public class B extends A
{
   @Override
   public void foo()
   {
     //some code
   }
 }
public class C extends A
{
   @Override
   public void foo()
   {
     //some code
   }
   @Override
   public boolean bar()
   {
      List<String> x=new ArrayList();
      x.add("a");
      //some code
   }
 }
public class D extends A
{
   @Override
   public void foo()
   {
     //some code
   }
 }

classes B, C and D run in different threads. however x is behaving like a shared memory for A and B and D. is it the expected behaviour? if yes how can i make it thread specific without overriding?

your example doesn't really show what's happening. You're going to have to put in more detail. What do you mean shared memory? What do you mean by "run"? — tom, Sep 15 '14 at 11:41
Maybe you wanted to make `x` a field? As a local variable it will never be _shared memory_ as local variables reside on the stack. — Seelenvirtuose, Sep 15 '14 at 11:42
@Seelenvirtouose: How to assign x as a field here, any clue? — Tarek, Sep 15 '14 at 11:45
@Seelenvirtuose How to make it a field? i am not able to figure out. — Parth Srivastav, Sep 15 '14 at 11:57
They are your classes. I was simply trying to figure out, what you are asking. With that code (containing `x` as a method's local variable) this question does not make sense. — Seelenvirtuose, Sep 15 '14 at 11:59
I will make an edit soon to make it clearer. thanks for the help and sorry for the inconvenience. — Parth Srivastav, Sep 15 '14 at 12:02
If you do not know "how to make [x] a field," then you probably are not ready to start messing with threads. You need to learn more about the basics of the language. (http://docs.oracle.com/javase/tutorial/java/javaOO/index.html) — Solomon Slow, Sep 15 '14 at 12:34
Classes are alwyas shared but they are stateless. It is instances of class which you share state across threads. — Peter Lawrey, Sep 15 '14 at 13:10

score 0 · Answer 1 · edited May 23 '17 at 12:21

0

the x variable is not being shared. It's replicated on any thread that invokes the bar() method. If its content is always the same, you should declare it as static final member variable. That is:

public abstract class A
{
 static final  List<String> x=new ArrayList();

Probably it'd also be a good idea to initialize it through a static initializer: Static initializer in Java

edited May 23 '17 at 12:21

Community

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answered Sep 15 '14 at 12:20

Andres

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abstract class as shared memory on different threads

1 Answers1