FindBugs

Its A Must-Have tool for every Java developer

FindBugs works similar to the Java compiler: as soon as you hit CTRL+S, Eclipse will compile the code and start incremental bug analysis. FindBugs can find an amazing number of different bug patterns, which are sometimes hard to debug or to reproduce. FindBugs has a very small number of false positives. Even if you think that the code will never run in the highlighted issue, in many cases the tool open your eyes on "dirty" places in your code.

FindBugs is valuable for both beginner and experienced programmers. If you just start to write Java applications, the tool will help you to learn better programming practices by explaining you the reasons why the code should be written in a different way. FindBugs helps experienced developers to keep the code clean and to review other's code by simply running the analysis over the Java projects.

FindBugs uses unique bytecode scanning techniques to analyze compiled Java code. In most cases the critical and medium severity bugs found by FindBugs are real, serious programming errors, and not just coding style issues. This is the main differentiator to other similar tools like PMD and Checkstyle (both are source-code analyzer).