Java Inheritance: How to declare a static variable in Super and instantiate it in subclass

Question

How would you declare a static variable in Super and instantiate it in subclass

Example

class A
{
  static Queue<String> myArray;

  public void doStuff()
  {
     myArray.add(someMethod.getStuff());
  } 

}
class B extends A
{
  myArray = new LinkedList<String>();

}

class C extends A
{
  myArray = new LinkedList<String>();

}

Obviously this doesnt work. But how would you go about declaring a variable; then doing some common functionality with the variable in the super class; Then making sure each subclass gets it own static LinkedList?

Why would you want to do this? What problem would this solve? — Jordan Kaye
– Jordan Kaye, Commented Oct 19, 2012 at 18:10
I want to have common functionality of array manipulation and have each subclass have its own static array. Therefore there will be two static arrays in total — stackoverflow
– stackoverflow, Commented Oct 19, 2012 at 18:13
In fact your first method itself will not compile. You are using static arrayList in non-static method.. — Rohit Jain
– Rohit Jain, Commented Oct 19, 2012 at 18:15

Louis Wasserman · Accepted Answer · 2012-10-19 18:07:20Z

5

You can't do stuff along these lines. The closest you can do is to have an abstract (non-static) method in the superclass and do some stuff with it.

But in general, you cannot force subclasses to do anything static, and you cannot access subclasses' static fields from a superclass like you're trying to do.

answered Oct 19, 2012 at 18:07

Louis Wasserman

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Comments

Nazar Merza · Accepted Answer · 2012-10-19 20:35:25Z

0

Since, you have subclass-specific properties to manipulate, you can't do it in the superclass, and it is not logical to do it anyways. As was already mentioned, you can do something like this:

abstract class A {
      public abstract void doStuff();       
    }

class B extends A    {
  static List<String>myArray = new LinkedList<String>();

  public abstract void doStuff() {
      // do B stuff
  }

}

class C extends A  {
  static List<String>myArray = new LinkedList<String>();
  public abstract void doStuff() {
      // do C stuff
  }

}

edited Oct 19, 2012 at 20:35

answered Oct 19, 2012 at 20:29

Nazar Merza

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Comments

Rohit Jain · Accepted Answer · 2012-10-19 18:07:30Z

0

Static variable is bound to a class rather than an instance. If you need a separate static variable for subclasses, you need to declare them in each of your subclasses.

answered Oct 19, 2012 at 18:07

Rohit Jain

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