Array Help

Question

I am writing a class that extends AbstractList. It is overriding the set(), get(), both add(), remove() , and size() functions. I am having a problem implementing this however. This class needs to create an array of objects that is variably sized, so the size is not set, it can constantly change. I was thinking of using two arrays, one that adds/removes an object, and another that is created afterwards, using System.arraycopy, and would be either 1 element larger or smaller depending on whether add or remove was called. I am just having some trouble implementing this because I have to initialize an array, but that array has to have a set size........ anyone have any ideas?

Answer 1

Well, this is basically how Sun does it in their ArrayList class.
(I ripped this straight from the sources):    public void ensureCapacity(int minCapacity) {
     int oldCapacity = elementData.length;
     if (minCapacity > oldCapacity) {
         Object oldData[] = elementData;
         int newCapacity = (oldCapacity * 3)/2 + 1;
             if (newCapacity < minCapacity)
          newCapacity = minCapacity;
         elementData = new Object[newCapacity];
         System.arraycopy(oldData, 0, elementData, 0, size);
    }The 'elementData' array holds the objects; it is replaced if it can't
contain at least 'minCapacity' elements.
kind regards,
Jos