Add a Method to Java 8 Stream

Question

While working with Java 8 Streams, I some times find that Stream doesn't have a particular method that I desire (e.g. takeWhile(), dropWhile(), skipLast()). How do I create my own stream class which has the additional methods with out re-writing the entire Java 8 Stream architecture?

I am aware of the StreamEx library and know that it has takeWhile() and dropWhile(). As of writing this, it doesn't have skipLast(). I have filed an issue for this method.

An acceptable solution would be to show how Java 8 Stream or StreamEx can be extended.

Answer 1

Since version 0.5.4 StreamEx library has a chain() method. This allows for creating helper methods which plug in comfortably.

public static <T> UnaryOperator<StreamEx<T>> skipLast(int n)
{
   return(stream -> skipLast(stream, n));
}

private static StreamEx<T> skipLast(Stream<T> input, int n)
{
   // implement the real logic of skipLast
}

With the above, one can now write...

StreamEx.
   of(input).
   chain(skipLast(10)).
   forEach(System.out::println);