<p>Actually I try to find a subclass of InputStream which is also Serializable. I think that doesn't exist. Since both Interfaces have many sublclasses it is hard to find one that is a subclass of both.</p>

<p>Until now I haven't found anything to help my search in Eclipse. Anyone ideas?</p>

<p>Edit: I understand now that serializing a Stream isn't really what one should do. But the essence of the Question is: how can I find a common subclass of two Interfaces.</p>

Serializing an InputStream is not a very viable solution. To illustrate this, imagine if you have an InputStream from a socket and you serialize that. Before you deserialize it, the socket is closed. Now when you actually do deserialize it, the resource has vanished and you have a nasty exception in your hands.
What you should rather do, if you need to serialize a resource, is to serialize the location of it or how to obtain it. In the socket example: host name and port, for files: the file path, etc.