Error: an enclosing instance that contains...

[phatslug311]

I'm gettin this error that says "an enclosing instance that contains abstractClass is required."

Basically abstractClass is a subclass, and from a different class, I'm trying to create a subclass that extends it.

An internet search didn't turn up much, except one confusing article which if I understood right said this error is some sort of bug in the compiler. I couldn't really understand it very well, so that might not be the case.

Anyway, if anyone knows anything about this problem help would be appreciated. And if I need to post more code, just tell me, but I have a feeling its not that specific of a problem.

[phatslug311]

Ok, heres the code anyway. The abstract subclass first:

    public abstract class UserDefinedElement extends Element{
        
        public UserDefinedElement(String token){ init(token); }
        protected HashMap getValueTable(){ return valueTable; }
        
        public abstract void init(String s);
        public abstract HashMap getExtraLookupValues();
        
    }

Now the subclass trying to extend it:

    private class foreachElement extends EqParser.UserDefinedElement {
        
        EqParser main;
        EqParser start;
        EqParser finish;
        
        private HashMap extraLookup;
        
        public void init(String key){
            String[] params = EqParser.getParams( key.substring(8, key.length()-1) );
            
            main = new EqParser(params[0]);
            start = new EqParser(params[2]);
            finish = new EqParser(params[3]);
            
            extraLookup.putAll(main.valueTable);
            extraLookup.putAll(start.valueTable);
            extraLookup.putAll(finish.valueTable);
            
            main.valueTable = getValueTable();
            start.valueTable =  getValueTable();
            finish.valueTable =  getValueTable();
        }
        
        public HashMap getExtraLookupValues() { return extraLookup; }
        
        public double getValue(){
            int intStart = new Double(start.Evaluate()).intValue();
            int intFinish = new Double(finish.Evaluate()).intValue();
            
            if (intFinish >= oldRaces.size()) intFinish = oldRaces.size()-1;

            double curValue = 0;
            for(int i = intStart; i<=intFinish; i++){
                main.valueTable.put("index", new Double(i));
                ((cOldRace)oldRaces.get(i)).FillValueTable(main);
                
                curValue += main.Evaluate();
            }
            
            return curValue;
        }
        
    }

Theres nothing special I don't think. The error is at the declaration of the foreachElement subclass. If I create a constructor for that class it moves to there. This is really gettin to me...

[sjalle]

What is Element ? I get compile-error for UserDefinedElement as the Element class
(defined in javax.swing.text.html.parser) is final (homemade ?).

And another thing, EqParser, is that a class and a package ??

[phatslug311]

Sorry for the confusion...

Element and UserDefinedElement are both subclasses of EqParser, which is just a class, not a package. Element extends DefaultMutableTreeNode.

If it helps at all to understand, EqParser is a class I'm writing that takes an equation (like "(x+5)/2") and sets up a tree of Elements(like values or operators) which can be quickly evaluated. The UserDefinedElement would be used outside of the class if I wanted to make EqParser understand something like "if(3<4,x+5)", so it needs to be overriden from outside of EqParser, which is where I seem to get this subclass extending another subclass error.

Anyway sjalle, thanks for even taking the time to read through my code (I know how much of a pain it is to try to understand someone else's) and lemme know if you have any clue what might be going on.

[sjalle]

This sounds like multiple inheritance to me, and I've only seen that in the
bloated hybrid OOP language called c++.

One way to achieve "multiple inheritance" is:
make an interface Z that defines all the methods of the X class that you need.
In your Y class (that extends WhatEver) you then have an object of class X.
Then define the Y class as extends WhatEver implements Z.
Then, in all the methods in Y that implements the Z interface you just call
the corresponding method for the X object.

I've made a mock version of your code that has the inheritance structure
that (I think) you described, some methods/variables may belong lower/higher
in this structure.

It may be useful, and maybe not....

import java.util.*;
import javax.swing.tree.*;

class EqParser
    extends DefaultMutableTreeNode {
  public EqParser() {}

  public EqParser(String s) {}

  public static String[] getParams(String s) {
    return null;
  }

  public HashMap valueTable = null;
  public int evaluate() {
    return 0;
  }
}

class Element
    extends EqParser {
  public Element() {}

  public ArrayList oldRaces = null;
}

class COldRace {
  public void FillValueTable(EqParser p) {}
}

abstract class UserDefinedElement
    extends Element {
  public UserDefinedElement() {}

  public UserDefinedElement(String token) {
    init(token);
  }

  protected HashMap getValueTable() {
    return valueTable;
  }

  public abstract void init(String s);

  public abstract HashMap getExtraLookupValues();

}

public class ForEachElement
    extends UserDefinedElement {

  EqParser main;
  EqParser start;
  EqParser finish;

  private HashMap extraLookup;

  public void init(String key) {
    String[] params = EqParser.getParams(key.substring(8, key.length() - 1));

    main = new EqParser(params[0]);
    start = new EqParser(params[2]);
    finish = new EqParser(params[3]);

    extraLookup.putAll(main.valueTable);
    extraLookup.putAll(start.valueTable);
    extraLookup.putAll(finish.valueTable);

    main.valueTable = getValueTable();
    start.valueTable = getValueTable();
    finish.valueTable = getValueTable();
  }

  public HashMap getExtraLookupValues() {
    return extraLookup;
  }

  public double getValue() {
    int intStart = new Double(start.evaluate()).intValue();
    int intFinish = new Double(finish.evaluate()).intValue();

    if (intFinish >= oldRaces.size())
      intFinish = oldRaces.size() - 1;

    double curValue = 0;
    for (int i = intStart; i <= intFinish; i++) {
      main.valueTable.put("index", new Double(i));
      ( (COldRace) oldRaces.get(i)).FillValueTable(main);

      curValue += main.evaluate();
    }

    return curValue;
  }

}

[phatslug311]

I get what you're saying, and it works, but its not exactly what I want here. I think its overcomplicated because I don't think I need multiple inheritance.

But basically I got my problem simplfied I think. Here's how to reproduce it. In NetBeans, create two classes.

The first class goes like this...

public class MainClass1 {
    
    public class Subclass1{
        
    }
}

Then create another class like this...

public class MainClass2 {
    
    public class Subclass2 extends MainClass1.Subclass1
        
    }
}

The declaration of Subclass2 will be underlined in red (error) and say "an enclosing instance that contains MainClass1.Subclass1 is required"

So what I doing wrong. Is this even possible?

[phatslug311]

Nevermind, I think I am talking about multiple inheritance, and your idea with an interface works just fine, so I think I'll use that.

Thanks for the help!

[Patrick Cosmo]

The problem is that Subclass1 is actually tied to an instance of a MainClass1 object - for example, it could be accessing data belonging to a specific instance of MainClass1.

So, you can't sub-class it without indicating which instance of MainClass1 you are sub-classing it for.

Anyways, if you make public class Subclass1 static, then the problem goes away (assuming that's what you want, that Subclass1 isn't really accessing non-static data belonging to MainClass1.

So, the fix is this:

public class MainClass1 {

static public class Subclass1{

}
}

public class MainClass2 {

public class Subclass2 extends MainClass1.Subclass1

}
}

hope that helps.