Question

I’m running into some trouble with nested classes on a project for school.
Currently, I’m trying to write a method to insert an item into a ragged array data structure.
It uses an object created by a nested class to keep track of the 2d array location in order to get the indexes to insert at. However, I am getting the error “The method findEnd(E) is undefined for the type RaggedArrayList.ListLoc” on the line:

insertLoc.findEnd(item)

I have searched extensively both on stackoverflow as well as around the web and have not found the answer yet. If I have missed it and this is redundant (there are a lot of “method undefined for type questions”, I know) then I apologize.

Here is the relevant code >>

nested class for ListLoc object:

private class ListLoc {
  public int level1Index;
  public int level2Index;

  public ListLoc() {}

  public ListLoc(int level1Index, int level2Index) {
     this.level1Index = level1Index;
     this.level2Index = level2Index;            
  }

  public int getLevel1Index() {
     return level1Index;
  }

  public int getLevel2Index() {
     return level2Index;
  }

  // since only used internally, can trust it is comparing 2 ListLoc's
  public boolean equals(Object otherObj) {
     return (this == otherObj);
  }
}

Method to find the last index of a matching item (not part of ListLoc nested class):

private ListLoc findEnd(E item){
  E itemAtIndex;

  for (int i = topArray.length -1; i >= 0; i--) {
     L2Array nextArray = (L2Array)topArray[i];

     if (nextArray == null) {
        continue;

     } else {

        for (int j = nextArray.items.length -1; j >= 0; j--) {
           itemAtIndex = nextArray.items[j];
           if (itemAtIndex.equals(item)) {
              return new ListLoc(i, j+1);
           }
        }
     }
  }

  return null;

}

Method attempting to add a new value to the ragged array:

boolean add(E item){
  ListLoc insertLoc = new ListLoc();
  insertLoc.findEnd(item);

  int index1 = insertLoc.getLevel1Index();
  int index2 = insertLoc.getLevel2Index();

  L2Array insertArray = (L2Array)topArray[index1];
  insertArray.items[index2] = item;

  return true;

}

Thanks for any input.

Answer 1

I’m going to bet that changing this:

ListLoc insertLoc = new ListLoc();
insertLoc.findEnd(item);

To this:

ListLoc insertLoc = findEnd(item);

Will fix your problem.

You’re trying to call findEnd on the ListLoc class, but if you actually look at ListLoc, it’s not defined there. When you tried to call findEnd on the insertLoc object, it fails because insertLoc is an instance of ListLoc, which we already said doesn’t contain findEnd.

That being said, I’m going to bet that findItem is actually declared in the same class as the add method (let’s just call it MyList), so you wanted to actually call MyList.findEnd, not the non-existent ListLoc.findEnd.