Most sophisticated code coverage tool for Java and Groovy.
Best Tools For Java
Browse 8 + Java Tools
OpenClover

Mariana Trench
Mariana Trench is a security focused static analysis platform targeting Android.

SikuliX
Automation of GUI components with mouse and keyboard actions.

Jubula
Jubula Functional Testing Tool for desktop Java applications

jUnit
#Unit Testing

TestNG
Java based testing framework

JPad
Java Scratchpad - Instantly write java snippets and see nicely formatted results.

Apache Jmeter
Open source load testing tool