Proper checked exception handling with lambda functions

I'm having trouble finding a clean way to handle checked exceptions thrown by a lambda function passed as a parameter in Java.

I'm writing a Client which will interact via RMI with a Server to play a game; a Client needs to be registered on the Server to be able to login, and it needs to be logged in to play a game. It's a college project, so I have some constraint on what technologies I can use and what I need to do. In particular, when a method raises a RemoteException I've been asked to retry to call the same method a few times. I'm using Java 8 and I wanted to experiment a little bit with lambdas.

The class I'm focusing on right now will be the interface the client will use to communicate with the server; as of now I have the following structure.

Note: most of the methods I need to implement are still to be written; I'm using a custom exception to remember to implement them.

ServerRMI.java

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface ServerRMI extends Remote {

    public static final String name = "hangman_server_rmi_name";

    public int login(String nick, String password)
        throws WrongPasswordException,
               RemoteException;

    public void logout(String nick, int cookie)
        throws UserNotLoggedException,
               RemoteException;

    public void register(String nick, String password)
        throws UserAlreadyRegisteredException,
               RemoteException;
}

ServerInterface.java

```
import java.net.InetAddress;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class ServerInterface {

private String nickname;
private InetAddress address;
private int port;
private ServerRMI serverRMI;

public ServerInterface(String nickname, InetAddress address, int port)
throws RemoteException, NotBoundException{
this.nickname = nickname;
this

Firstly, a couple of comments:

ServerInterface is a bad name for something that isn't an interface.

Why do you have //\ before your lambda's body? Java is perfectly content with having it on a new line. As far as I can tell, this is useless.

Now, with regards to your actual question: Yes, you can do exactly that. It's literally that syntax. You can also put multiple catch blocks, so instead of that instanceof mess, you can have this:

catch (RemoteException | NotBoundException e) {
    throw e;
} catch (Exception e) {
    throw new RuntimeException("Unexpected exception");
}

It checks each in order, and subclasses are caught with any statement that matches their superclass.

Now, there are a couple of issues with your approach:

• You're throwing a plain RuntimeException. This is typically a bad idea, because if you throw a more specific one, people can catch situations where their own exceptional case occurs.

• You don't give any information about what caused the exception, neither in the message nor through the exception itself.

You can fix both problems by either:

• Creating your own custom exception class that carries the information, or

-
Use the RuntimeException(String, Throwable) constructor, and use a more informative message. That call would look something like:

throw new RuntimeException("Unexpected exception: " + e.getMessage(), e);

Aside from that, I can't see that much wrong with your code. Once I get a chance I'll run it through Eclipse and see if it turns up anything -- if I haven't in 24 hours or so, please reply here and remind me.

StackExchange Code Review Q#93988, answer score: 3