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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); }

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.

Inspection Details

By default bundled with:

IntelliJ IDEA 2024.1, Qodana for JVM 2024.1,

Can be installed with plugin:

Java, 241.16690

Last modified: 29 April 2024