Can you split a stream into two streams?

Question

I have a data set represented by a Java 8 stream:

Stream stream = ...;

I can see how to filter it to get a random subset - for exa

Answer 1

Unfortunately, what you ask for is directly frowned upon in the JavaDoc of Stream:

A stream should be operated on (invoking an intermediate or terminal stream operation) only once. This rules out, for example, "forked" streams, where the same source feeds two or more pipelines, or multiple traversals of the same stream.

You can work around this using peek or other methods should you truly desire that type of behaviour. In this case, what you should do is instead of trying to back two streams from the same original Stream source with a forking filter, you would duplicate your stream and filter each of the duplicates appropriately.

However, you may wish to reconsider if a Stream is the appropriate structure for your use case.