The whole idea of the Stream is that it's once-off. This allows you to create non-reenterable sources (for example, reading the lines from the network connection) without intermediate storage. If you, however, want to reuse the Stream content, you may dump it into the intermediate collection to get the "hard copy":
Stream stream = // get the stream from somewhere
List list = stream.collect(Collectors.toList()); // materialize the stream contents
list.stream().doSomething // create a new stream from the list
list.stream().doSomethingElse // create one more stream from the list
If you don't want to materialize the stream, in some cases there are ways to do several things with the same stream at once. For example, you may refer to this or this question for details.
