Implementation Class for RMI App, Compile-Time Error

[Jacob1028555]

When I try to compile my class for my RMI Implementation, called ServiceServerImpl, I get these two errors when I try to compile, here is the Shell:

[jacob@localhost Source]$ javac -d ../Classes *.java
ServiceServerImpl.java:5: '{' expected
public interface ServiceServerImpl extends UnicastRemoteObject implements ServiceServer {
                                                              ^
ServiceServerImpl.java:8: <identifier> expected
        public ServiceServerImpl() throws RemoteException {
                                ^
2 errors

PLEASE HELP!!!!!!!!!!!!!!!!!!!

[Jacob1028555]

BTW, here is the class code:

import java.rmi.*;
import java.util.*;
import java.rmi.server.*;

public interface ServiceServerImpl extends UnicastRemoteObject implements ServiceServer {
	HashMap serviceList = new HashMap();
	
	public ServiceServerImpl() throws RemoteException {
		setUpServices();
	}
	
	public void setUpServices() {
		serviceList.put("Calculator Service", new CalculatorService());
		serviceList.put("Alphabetizer Service", new AlphabetizerService());
		serviceList.put("Text Editor Service", new TextEditorService());
		serviceList.put("Visual Music Service", new VisualMusicService());
		serviceList.put("Chatting Service", new ChattingService());
	}
	
	public Object[ ] getServiceList() {
		System.out.println("In Remote");
		return serviceList.keySet().toArray();
	}
	
	public Service getService(Object serviceKey) throws RemoteException {
		Service theService = (Service) serviceList.get(serviceKey);
		return theService;
	}
	
	public static void main(String args[ ]) {
		try {
			Naming.rebind("ServiceServer", new ServiceServerImpl());
		} catch(Exception ex) {
			ex.printStackTrace();
		}
		System.out.println("Remote Service Is Running");
	}
}

[Norm]

Are you defining an interface or a class?

[JosAH]

An interface doesn't implement anything; it can just extend other interfaces. b.t.w. the code you showed us is a class definition, not an interface.

kind regards,

Jos

[Jacob1028555]

Thanks, but I changed it from interface, to class and a new problem arose:

[jacob@localhost Source]$ javac -d ../Classes *.java
ServiceBrowser.java:62: ServiceBrowser.MyListListener is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener
        class MyListListener implements ActionListener {

in the class:

import java.awt.*;
import java.rmi.*;
import java.awt.event.*;
import javax.swing.*;

public class ServiceBrowser {
	Panel mainPanel;
	JComboBox serviceList;
	ServiceServer server;
	
	public void buildGui() {
		Frame frame = new Frame("Science Fair :: RMI Browser");
		mainPanel = new Panel();
		frame.add(BorderLayout.CENTER, mainPanel);
		
		Object[ ] services = getServicesList();
		
		serviceList = new JComboBox(services);
		
		frame.add(BorderLayout.NORTH, serviceList);
		
		serviceList.addActionListener(new MyListListener());
		
		frame.setSize(500, 500);
		frame.setVisible(true);
	}
	
	void loadService(Object serviceSelection) {
		try {
			Service svc = server.getService(serviceSelection);
			
			mainPanel.removeAll();
			mainPanel.add(svc.getGuiPanel());
			mainPanel.validate();
			mainPanel.repaint();
		} catch(Exception ex) {
			ex.printStackTrace();
		}
	}
	
	Object[ ] getServicesList() {
		Object obj = null;
		Object[ ] services = null;
		
		try {
			obj = Naming.lookup("rmi://192.168.0.183/ServiceServer");
		} catch(Exception ex) {
			ex.printStackTrace();
		}
		server = (ServiceServer) obj;
		
		try {
			services = server.getServiceList();
		} catch(Exception ex) {
			ex.printStackTrace();
		}
		
		return services;
		
	}
	
	class MyListListener implements ActionListener {
		public void actionPreformed(ActionEvent ev) {
			Object selection = serviceList.getSelectedItem();
			loadService(selection);
		}
	}
	
	public static void main(String[ ] args) {
		new ServiceBrowser().buildGui();
	}
}

Sorry, I am rather new at the RMI stuff.

[Jacob1028555]

[Norm]

Nothing to do with RMI.
Where is the MyListListener class definition? You don't show it.


When your class implements an interface, you are required to define all the methods defined in the interface.
Does your code do that? Read the API doc for the interface and get the specs on what methods it uses.
To check for spelling errors, put an @Override statement before the method definition.

[Jacob1028555]

Whaa???? [JosAH: huge image removed]

[Norm]

Go back to your tutorial or text and read about how to use an interface.

[Jacob1028555]

My book that I learned out of, nor the tutorial I just read say anything about class definitions for interfaces.
I'm sorry to be such a stick in the mud.

[Norm]

Go back and read the error messge text:

does not override abstract method actionPerformed

That tells you what is wrong. Your code does not override a method in the interface.

There is also google. Try googling this: java class implements interface

[Jacob1028555]

Should I use the @Override Annotation then???

[Norm]

@Override is a statement asking the compiler to check if the following method definition is indeed overriding a method.

Yes it is a good idea to use it. Before it was available, a simple typo of a method name could cost a lot of time finding out why a listener was not being called. That was mainly when using Adaptors which define all the methods with empty methods. When using an implements, the compiler will check for all required methods; As you see with your error.

[Jacob1028555]

Okay, I get that, but then what else is required there??
Sorry for being a pain in the butt, the book never said anything about this.
I checked the docs for ActionListener, and the only method there was actionPreformed(ActionEvent). And I checked the SuperInterface for it and it had no methods.
I AM CONFUSED!!!!!!!!!

[Norm]

the only method there was actionPreformed(ActionEvent)

ReRead the error message:

does not override abstract method actionPerformed

Look at it letter by letter.

[Jacob1028555]

Please!! Enough with the cryptic messages. Just tell me what I did wrong, so I don't do it again!!

[Jacob1028555]

Sorry to be so rude in the last post. I am starting to get frustrated because the answer is right there, but I don't get it. Part of the problem is that i am teaching this to myself. From a book: Head First Java 2nd Edition.

[Norm]

Sorry, you need to learn to look at your code and find your errors. I'm not going to tell you what is wrong. But I will tell you where to look. You'll need to learn to do things at this level of detail if you want to learn to program.

Did you look at what I pasted above? And compare it with the text of the error message? Letter by letter?

[Norm]

Did you use the @Override statement in front of your listener method?
What did it say?

[Jacob1028555]

Thank You for your time and Effort. I really am trying to learn. and I appreciate your help.