code: @Throws(IllegalPositionIndexException.class)
  	public static int positionIndex(final int index, final int size) {
  		final boolean isIndexValid = (size >= 0) && (index >= 0) && (index < size);
  
  		if (!isIndexValid) {
  			throw new IllegalPositionIndexException(index, size);
  		}
  
  		return index;
  	}
docs: Ensures that a given position index is valid within the size of an array, list or string ...
  
  @param index
  index of an array, list or string
  @param size
  size of an array list or string
  @return the index
  
  @throws IllegalPositionIndexException
  if the index is not a valid position index within an array, list or string of size <em>size</em>