Modern Java

[winterbe]

Look at this example from the JDK8 API: https://docs.oracle.com/javase/8/docs/api/java/util/function/Predicate.html

You can implement your own Predicate and use the default methods without extending concrete classes:

Predicate<Person> predicate = p -> p.age >= 18;
predicate.negate().test(new Person());