Also known as the Java 8 Predicate -- which stems from the JDK version where functional programming was introduced to developers -- this simple interface defines five methods, although only the Java ...

One of the great evolutions in Java was the introduction of streams and lambdas in Java 8 ... the method reference operator (the double colon) to refer to the System.out::println() function.

Only functional interfaces can use the lambda feature ... Can have default and static methods (introduced in Java 8). Can have private methods with the implementation (introduced in Java 9).

The java.util.function.Consumer class has one non-default method named accept which takes a single ... defined in this package follow all of the standard, pre Java 8 rules for implementing interfaces.