code: @Override
      public void setIndex(int currentIndex) throws IndexOutOfBoundsException{
          if (currentIndex < 0 || currentIndex > replaceable.length()) {
              throw new IndexOutOfBoundsException();
          }
          this.currentIndex = currentIndex;
      }
docs: <p>Sets the currentIndex to the specified currentIndex in the text and returns that
  single UTF16 character at currentIndex.
  This assumes the text is stored as 16-bit code units.</p>
  @param currentIndex the currentIndex within the text.
  @exception IllegalArgumentException is thrown if an invalid currentIndex is
  supplied. i.e. currentIndex is out of bounds.
  @returns the character at the specified currentIndex or DONE if the specified
  currentIndex is equal to the end of the text.