A DESCRIPTION OF THE REQUEST :
From the usage of java.net.URLStreamHandlerFactory.createURLStreamHandler() in java.net.URL it is clear that createURLStreamHandler() is supposed to return null when it doesn't know how to handle the protocol. The documentation doesn't mention that; it says that it must return a URLStreamHandler instance for the specified protocol.

JUSTIFICATION :
The current documentation implies that a URLStreamHandlerFactory must return URLStreamHandler for every possible protocol, which doesn't make sense.