Problem building Mobile Designer Project using JDK 6

Hi, I am trying to build a mobile application using Mobile Designer and have used generics in my code. When i first tried to run “Activate Handset”, it gave me an exception saying the source is JDK 1.3 which does not support generic. I modified the file bs-defaults located in /Tools/Build/BuildScript/v1.0.0 as follows

But now I am getting the following error cannot access java.lang.StringBuilder
[javac] class file for java.lang.StringBuilder not found
[javac] init_url = conn.getProtocol () + “://” + conn.getHost () + “:” + conn.getPort () + init_url;


Is there any other file I need to change to make the app compatible with java 1.6 or higher.