code: public int lastIndexOf(Object o) {
          if (o == null) {
              for (int i = size-1; i >= 0; i--)
                  if (elementData[i]==null)
                      return i;
          } else {
              for (int i = size-1; i >= 0; i--)
                  if (o.equals(elementData[i]))
                      return i;
          }
          return -1;
      }
docs: Returns the index of the last occurrence of the specified element
  in this list, or -1 if this list does not contain the element.
  More formally, returns the highest index <tt>i</tt> such that
  <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,
  or -1 if there is no such index.