How can I check if an InputStream is empty without reading from it?

No, you can't. InputStream is designed to work with remote resources, so you can't know if it's there until you actually read from it.

You may be able to use a java.io.PushbackInputStream, however, which allows you to read from the stream to see if there's something there, and then "push it back" up the stream (that's not how it really works, but that's the way it behaves to client code).

I think you are looking for inputstream.available(). It does not tell you whether its empty but it can give you an indication as to whether data is there to be read or not.