In case you want to quickly find out which of your Java threads is the culprit in a JVM's high CPU usage, this tool is truly helpful.
Simply download topthreads.jar from http://lsd.luminis.nl/top-threads-plugin-for-jconsole/
and run your jconsole like this:
jconsole -pluginpath topthreads.jar
Similar to 'jtop', just a little better.