Can I upgrade the JDK version?

Simple answer: no. IBM has customized the basic Java development kit reference implementation provided by Sun to allow several very nice advantages, like incremental compilation and incremental debugging.

You need to wait for IBM to release a patch for the next Java language version.

Note that IBM is very aware that this is a major issue for many people and have stated that they are working on ways to provide more timely updates for the JDK.