Introduction to Programming

Stream operations

Many of the methods of the Stream interface (those that have a functional interface type as a parameter) are called operations, because they are not implemented as traditional methods. Their functionalities are passed into the methods as a functions. The methods themselves are just shells that call a method of the functional interface, assigned as the type of the method parameter.

For example, let us look at the Stream<T> filter (Predicate<T> predicate) method. Its implementation is based on the call to the boolean test(T) method of the Predicate<T> function. So, instead of saying, "We use the filter() method of the Stream object to select some of the stream elements and skip others," the programmers prefer to say, "We apply ...