IntellJ IDEA

IntellJ IDEA is a commercial Java IDE (integrated development environment) that also offers a free and open source (FOSS) community version.

IntellJ is sometimes referred to as an intelligent IDE. It indexes projects in their entirety, analyses their content and builds a syntax tree. That makes it possible for the IDE to understand any area where a programmer starts in and know what types of things can be done at that point.

The lightweight IDE offers JUnit and TestNG testing, code inspections, code completion, support for multiple refactoring, Maven and Ant build tools, a visual GUI (graphical user interface) builder and a code editor for XML as well as Java. The commercial version, called the Ultimate Edition, introduces support for Python, Ruby and JavaScript, with Node.js and PHP available via separate plug-ins.

IntellJ provides the foundation for a number of prominent applications, including Google's Android Studio. Other popular Java IDEs include Eclipse and NetBeans.