Basic stream/file/socket closing question

Question

If you create a stream, it's generally considered good practice to call close() on that stream once you're done with it. the same for files and sockets. My question is what happens if I don't keep a reference to the object that needs closing. For example:
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(new File("myfile.txt")));Clearly, I can close() bis. But does doing so close the FileInputStream, and the File? OR, will those remain open until the garbage collecter gets around to closing them. If not, is it considered good practice to keep references around for the sole purpose of explicitly closing the resource so you don't have to wait for garbage collection?
Finally, is it necessary to close() sockets/files/streams prior to calling System.exit()? It would save me a great deal of code in my exception handlers if I could simply exit() without explicitly freeing the resources I've opened prior to hitting the exception.
Thanks.

Answer 1

You should only need to call close on bis. That method call should take care of calling close on the underlying stream.