Then FP became the hot new shit, so they all added some of the lowest hanging fruit so that people can say absolutely weird things like "I do FP in C#". The problem is that the majority of these implementations just eagerly iterate the collection and make full copies every time. So, you're much better off with a for-loop.
To be fair to GP, though, Java has legit engineering behind it, and the way they did it was to introduce the Stream API, which is lazy sequences, and they made the compiler smart enough to avoid actually allocating a new Stream object per method call (which is what the code nominally does, IIRC- each method wraps the original Stream in a new Stream object that holds on to the closure argument and applies on each iteration).
