IntelliJ IDEA is a commercial Java IDE by JetBrains, often referred simply as IntelliJ.
The latest version of IntelliJ (11.1) includes a number of advanced features such UML-like class diagrams, visual Hibernate modeling, Spring 3.0 and Play Framework support, Dependency and Data Flow Analysis, Apache Maven support, Intelligent Coding Assistance and On-the-fly Code Analysis. A complete list can be found at their features page.
Jetbrains provides a fully functional 30-day trial version of the commercial edition for various platforms. Also available is an open source Community Edition. Check the differences between commercial and community versions here.
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