Interface may be annotated as '@FunctionalInterface'

Reports interfaces that can be annotated with @FunctionalInterface (available since JDK 1.8).

Annotating an interface with @FunctionalInterface indicates that the interface is functional and no more abstract methods can be added to it.

Example:

  interface FileProcessor {
    void execute(File file);
  }

After the quick-fix is applied:

  @FunctionalInterface
  interface FileProcessor {
    void execute(File file);
  }

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

InterfaceMayBeAnnotatedFunctional

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Java | Class structure

This inspection only reports if the language level of the project or module is 8 or higher.

This inspection depends on the Java feature 'Lambda expressions' which is available since Java 8.

Last modified: 18 June 2024