IntelliJ IDEA

What IntelliJ IDEA is

IntelliJ IDEA is an integrated development environment (IDE) from JetBrains, built first for Java and Kotlin. It understands your code deeply: it knows every class, method and reference in the project, which is what makes its code navigation, inspections and refactorings so reliable.

Free or paid?

Starting with version 2025.3, JetBrains combined the former Community Edition and Ultimate into a single, unified product. According to JetBrains, everything that was in the Community Edition remains free, and the free core now includes more than before. New users can try the extended features with a free 30-day trial and then keep using IntelliJ IDEA for free for core Java and Kotlin development. A subscription unlocks the advanced features, such as deeper framework support. JetBrains also runs a free educational licensing programme for students; check its current terms on the JetBrains site.

For everything in a software design roadmap, the free core is enough.

Why it matters for learning design

Refactoring only works when changes are small and safe, and doing them by hand is slow and error prone. IntelliJ IDEA automates the common refactorings. Its documentation lists, with Windows and Linux shortcuts:

• Refactor This (Ctrl+Alt+Shift+T): a menu of every refactoring available at the caret.
• Rename (Shift+F6): updates every reference across the project.
• Extract Method (Ctrl+Alt+M), Extract Constant (Ctrl+Alt+C), Extract Field (Ctrl+Alt+F), Extract Parameter (Ctrl+Alt+P) and Introduce Variable (Ctrl+Alt+V).
• Inline (Ctrl+Alt+N): the reverse of extract.
• Change Signature (Ctrl+F6), Move (F6), Copy (F5) and Safe Delete (Alt+Delete).

Learning these shortcuts turns refactoring from a risky afternoon into a series of safe, second-long steps.

Other features you will use

Inspections flag likely bugs and code smells as you type, and many come with a quick fix. The debugger, test runner and Git integration are built in. Code generation writes constructors, equals and hashCode, though in modern Java a record often replaces them.

Common questions

IntelliJ IDEA or VS Code for Java? VS Code with Java extensions works, but IntelliJ IDEA's refactorings and inspections are deeper, which matters when you are learning to refactor.

Does it work for other languages? It is focused on Java and Kotlin; JetBrains makes separate IDEs such as PyCharm for Python and Rider for .NET.

Best for: Java learners and professionals who want the strongest automated refactoring support.