Additional method on Stream

[Stephen Colebourne]

This is a request for an additional method on java.util.stream.Stream.

Having written quite a bit of code in Java 8 now, one annoyance keeps
on coming up, filtering and casting the stream.

Currently, it is necessary to do this:

    return input.stream()
        .filter(Foo.class::isInstance)
        .map(Foo.class::cast)
        .someTerminalOperation();

or

    return input.stream()
        .filter(t -> t instanceof Foo)
        .map(t -> (Foo) t)
        .someTerminalOperation();

Really, what is needed is this:

    return input.stream()
        .filter(Foo.class)
        .someTerminalOperation();

For info, Guava's FluentIterable has such a method.

The new method signature would be something like:

public Stream<R> filter(Class<R> cls);

As far as I can see, there is no problem in implementing this in both
serial and parallel modes, as it is essentially just a convenience.

Thoughts?
Stephen