@Documented @Retention(RUNTIME) @Target(TYPE) public @interface FunctionalInterface
java.lang.Object, that also does not count toward the interface's abstract method count since any implementation of the interface will have an implementation from
Note that instances of functional interfaces can be created with lambda expressions, method references, or constructor references.
If a type is annotated with this annotation type, compilers are required to generate an error message unless:
However, the compiler will treat any interface meeting the
definition of a functional interface as a functional interface
regardless of whether or not a
annotation is present on the interface declaration.
Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2017, Oracle and/or its affiliates. 500 Oracle Parkway
Redwood Shores, CA 94065 USA. All rights reserved.