The SQE NetBeans plugin seems excellent. It provides Code defect analysis tools such as : FindBugs PMD CheckStyle Lint4J and metrics & dependency analysis tool. It's is easy to add to NetBeans 6.5.1. I just added their link : https://sqe.dev.java.net/updatecenters/sqe/updates.xml to my update centre and then was able to choose the SQE options to download. FindBugs & PMD are both excellent at finding potential issues with your Java code.
VisualVM is a visual tool integrating several commandline JDK tools and lightweight profiling capabilities. Designed for both production and development time use, it further enhances the capability of monitoring and performance analysis for the Java SE platform VisualVM home VisualVM release notes dzone: visual vm 1.1 now available
NetBeans 6.5 released NetBeans: New Features Lots of new features and new support for various languages and environments. New for Java SE is : * Automatic Compile on Save * Improved Eclipse project import and synchronization * Java Call Hierarchy * Analyze Javadoc * Swing GUI Builder can generate simple or fully qualified class names
Java diagnostics, IBM style, Part 1: Introducing the IBM Dump Analyzer for Java "Cut through endless dump files to get to the heart of the problem" An interesting article about the IBM Dump Analyzer for Java IBM developerWorks article link