Generating UML Class Diagrams in IntelliJ IDEA

When working on Java projects, you may want to visualize existing code as UML class diagrams. IntelliJ IDEA includes a built‑in Diagram plugin that can generate these diagrams automatically, similar to PlantUML but without external tools.

First, open the settings via File → Settings (or press Ctrl+Alt+S on Windows). In the search box type "Diagram" and locate the UML settings.

In the "Java Class Diagrams" section, enable the checkboxes for the elements you need—typically members, constructors, and methods. After applying the settings, you can generate a diagram for any class.

Select the desired Java class file in the editor, then press Ctrl+Shift+Alt+U (or Ctrl+Alt+U) or right‑click and choose the generate option. The UML diagram will appear, showing the class structure.

The generated diagram includes the class name, fields, constructors, and methods as selected. You can also generate diagrams for entire packages, such as the support package, using the same shortcut.

Limitations: the automatic generation works only from existing code, so it cannot be used for forward‑design of classes. Professional UML tools may produce more precise and customizable diagrams, which is important for strict UML requirements.