Within each iteration, the iteration count will be stored in Param.pyForEachCount

So, you can use this parameter to compare the current element with the previous element.

Also If you can share the sample JSP code you are using to the thread, it will be better to guide you.

You can use the below code in a  java step or in a function . You can remove SamplePage and SamplePageListProperty with a page name and a page list property respectively . 

ClipboardProperty ClipboardProp = SamplePage.getProperty("SamplePageListProperty");
java.util.ListIterator IteratorTmp = ClipboardProp.iterator();
while(IteratorTmp.hasNext()) 
{
 String CurrentValue=IteratorTmp.next();  # Current Value 
 String PrevoiusValue=IteratorTmp.previous(); # Previous Value
}

Please attach the screenshot of the code u r using for advising you further.