code: @SuppressWarnings("unchecked")
      public <T extends XPathBuilder> T setResultIdx(final Position resultIdx) {
          this.resultIdx = resultIdx.getValue();
          return (T) this;
      }
docs: <p><b>Used for finding element process (to generate xpath address)</b></p>
  <p>Result Example:</p>
  <pre>
  (//*[contains(@class, 'x-grid-panel')])[last()]
  </pre>
  More details please see: http://stackoverflow.com/questions/4961349/combine-xpath-predicate-with-position
  
  @param resultIdx {@link Position}
  @param <T>       the element which calls this method
  @return this element