How should i know which exception should i catch?

Question

hey all....
i am getting the following error msgs (everything is compiled just fine..)
I successfully translated the word car to αυτοκίνητο
15 &#916;&#949;&#954; 2006 5:28:40 &#956;&#956; com.sun.corba.se.impl.transport.SocketOrChannelConnectionImpl <init>
WARNING: "IOP00410201: (COMM_FAILURE) Connection failure: socketType: IIOP_CLEAR_TEXT; hostname: 10.34.153.11; port: 1541"
org.omg.CORBA.COMM_FAILURE:   vmcid: SUN  minor code: 201  completed: No
     at com.sun.corba.se.impl.logging.ORBUtilSystemException.connectFailure(Unknown Source)
     at com.sun.corba.se.impl.logging.ORBUtilSystemException.connectFailure(Unknown Source)
     at com.sun.corba.se.impl.transport.SocketOrChannelConnectionImpl.<init>(Unknown Source)
     at com.sun.corba.se.impl.transport.SocketOrChannelConnectionImpl.<init>(Unknown Source)
     at com.sun.corba.se.impl.transport.SocketOrChannelContactInfoImpl.createConnection(Unknown Source)
     at com.sun.corba.se.impl.protocol.CorbaClientRequestDispatcherImpl.beginRequest(Unknown Source)
     at com.sun.corba.se.impl.protocol.CorbaClientDelegateImpl.request(Unknown Source)
     at org.omg.CORBA.portable.ObjectImpl._request(Unknown Source)
     at WorkflowFramework._ServiceStub.translationService(_ServiceStub.java:18)
     at wF.ServantEnglishToGreek.translationService(ServantEnglishToGreek.java:294)
     at WorkflowFramework._ServiceImplBase._invoke(_ServiceImplBase.java:41)
     at com.sun.corba.se.impl.protocol.CorbaServerRequestDispatcherImpl.dispatchToServant(Unknown Source)
     at com.sun.corba.se.impl.protocol.CorbaServerRequestDispatcherImpl.dispatch(Unknown Source)
     at com.sun.corba.se.impl.protocol.CorbaMessageMediatorImpl.handleRequestRequest(Unknown Source)
     at com.sun.corba.se.impl.protocol.CorbaMessageMediatorImpl.handleRequest(Unknown Source)
     at com.sun.corba.se.impl.protocol.CorbaMessageMediatorImpl.handleInput(Unknown Source)
     at com.sun.corba.se.impl.protocol.giopmsgheaders.RequestMessage_1_2.callback(Unknown Source)
     at com.sun.corba.se.impl.protocol.CorbaMessageMediatorImpl.handleRequest(Unknown Source)
     at com.sun.corba.se.impl.transport.SocketOrChannelConnectionImpl.dispatch(Unknown Source)
     at com.sun.corba.se.impl.transport.SocketOrChannelConnectionImpl.doWork(Unknown Source)
     at com.sun.corba.se.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.run(Unknown Source)
Caused by: java.net.ConnectException: Connection refused: connect
     at sun.nio.ch.Net.connect(Native Method)
     at sun.nio.ch.SocketChannelImpl.connect(Unknown Source)
     at java.nio.channels.SocketChannel.open(Unknown Source)
     at com.sun.corba.se.impl.transport.DefaultSocketFactoryImpl.createSocket(Unknown Source)
     ... 19 more
NEXT SERVER IS DOWN! org.omg.CORBA.COMM_FAILURE:   vmcid: SUN  minor code: 201  completed: No when i am running a function on a remote object reference
i have catched the exception and that is why the msg NEXT SERVER IS DOWN is printed..but how can i handle all the previous msgs?
i searched a lot on the internet and i cannot find how to catch this error...
all these msg seem to come from the java.net.ConnectException: Connection refused: connect but i dont have any statement that i can include in a catch try block so that i can do sth with that..(maybe print a msg..)
btw the line from my code that this msg is refering to is the following
try{
     //call next server
        nextServerRef.translationService(objRef, buffer);
//      catch(java.net.ConnectException e){
catch(Exception e){
          System.out.println("NEXT SERVER IS DOWN! "+e);
           }and btw i cannot include this code to the ConnectException because it keeps complaining that this code cannot throw this exception....
any advice????
ps.i have posted a specific msg to the rmi subforum...but i am trying to undestand the general process ..to look the wood not the trees;-)

Answer 1

If the runtime exception occurs in a method that doesn't either catch it or declare it as being thrown, and you can't change the method, then there's not much you can do except diverting the output to a non-visible location, or a null sink.
If you can change the method, you can either catch the exception and substitute your message, or you can change it to throw the method, and then catch the exception in a higher enclosing method, as I show:
public static void main(String[] args)
    try
        some_method();
    catch (ConnectException ce)
        System.out.println("NEXT SERVER IS DOWN");
static void some_method() throws ConnectException
    throw new ConnectException(); // create the exception
}