When a Function object’s input type is the same as its output type, an Operator interface can be used in place of a Function. Operator interfaces define a single type parameter.
Section 5.1: The UnaryOperator Interface
UnaryOperator
is a functional interface with one type parameter such that UnaryOperator<T> inherits Function<T, T>. Like Function, a lambda expression that represents the apply method with a single argument must be provided. UnaryOperator supports andThen, compose, and identity
as well. It is useful for implementing operations on a single operand.
@FunctionalInterface
public ...
