2.3 The Distributed and Nondistributed Models Contrasted

The Java platform's distributed object model is similar to the Java platform's object model in the following ways:

• A reference to a remote object can be passed as an argument or returned as a result in any method invocation (local or remote).
• A remote object can be cast to any of the set of remote interfaces supported by the implementation using the syntax for casting built into the Java programming language.
• The built-in instanceof operator can be used to test the remote interfaces supported by a remote object.

The Java platform's distributed object model differs from the Java platform's object model in these ways:

• Clients of remote objects interact with remote interfaces, never with the implementation classes of those interfaces.
• Non-remote arguments to, and results from, a remote method invocation are passed by copy rather than by reference. This is because references to objects are only useful within a single virtual machine.
• A remote object is passed by reference, not by copying the actual remote implementation.
• The semantics of some of the methods defined by class java.lang.Object are specialized for remote objects.
• Since the failure modes of invoking remote objects are inherently more complicated than the failure modes of invoking local objects, clients must deal with additional exceptions that can occur during a remote method invocation.