Getting distinct Values from XML using XPath

[Udit Manektala]

So I need to retrieve distinct values for the Source Element in this XML.
I identified 2 ways:

<RESPONSE>
  <RECORD>
    ...
    ...
    <SOURCE>A</SOURCE>
  </RECORD>
  <RECORD>
    ...
    ...
    <SOURCE>B</SOURCE>
  </RECORD>
  <RECORD>
    ...
    ...
    <SOURCE>A</SOURCE>
  </RECORD>
</RESPONSE>

1. A function called distinct-values. Gave an exception. Here's how i tried it:

List lList1 = inputXML.selectNodes("distinct-values(//RESPONSE/RECORD/SOURCE)");

2. I tried a method i took from
this website
link
Here;s how I tried to implement it:

List lList1 = inputXML.selectNodes("/RESPONSE/RECORD/SOURCE[not( text()=preceding-sibling::RECORD/SAMPLESOURCE/text())]/text()  ");

The problem with the second method is that i need to look for the preceding sibling of the parent and not the preceding sibling of the SOURCE Element. And I cant find a function for finding the parent element.

[Udit Manektala]

fixed it:

List lList1 = inputXML.selectNodes("/RESPONSE/RECORD[not( SOURCE/text()=preceding-sibling::RECORD/SOURCE/text())]/SOURCE/text() ");

Anyone know a better way ?

But still can't figure out what the Object Type of the thing is thats stored in the List.