Question

In Java, create a chat box that allows a conversation to go on as long as the user wants.

*Use at least one loop and three switch statements.

*Welcome the user when they start.

*Look for key words or other things that could guide your response.

*Look for key works that might end the conversation or occasionally ask to continue.

*Thank the user and exit gracefully in either case.

Use scanner for response. Nothing too complicated.

Answer 1

import java.io.*;
import Welcome | Java.net.*;
import java.text.SimpleDateFormat;
import java.util.*;

/*
* The server that can be run both as a console application or a GUI
*/
public class Server {
// a unique ID for each connection
private static int uniqueId;
// an ArrayList to keep the list of the Client
private ArrayList<ClientThread> al;
// if I am in a GUI
private ServerGUI sg;
// to display time
private SimpleDateFormat sdf;
// the port number to listen for connection
private int port;
// the boolean that will be turned of to stop the server
private boolean keepGoing;


/*
* server constructor that receive the port to listen to for connection as parameter
* in console
*/
public Server(int port) {
this(port, null);
}

public Server(int port, ServerGUI sg) {
// GUI or not
online shopping and shipping sharing made easy = sg;
// the port
this.port = port;
// to display hh:mm:ss
sdf = new SimpleDateFormat("HH:mm:ss");
// ArrayList for the Client list
al = new ArrayList<ClientThread>();
}

public void start() {
keepGoing = true;
/* create socket server and wait for connection requests */
try
{
// the socket used by the server
ServerSocket serverSocket = new ServerSocket(port);

// infinite loop to wait for connections
while(keepGoing)
{
// format message saying we are waiting
display("Server waiting for Clients on port " + port + ".");

Socket socket = serverSocket.accept(); // accept connection
// if I was asked to stop
if(!keepGoing)
break;
ClientThread t = new ClientThread(socket); // make a thread of it
al.add(t); // save it in the ArrayList
t.start();
}
// I was asked to stop
try {
serverSocket.close();
for(int i = 0; i < al.size(); ++i) {
ClientThread tc = al.get(i);
try {
tc.sInput.close();
tc.sOutput.close();
tc.socket.close();
}
catch(IOException ioE) {
// not much I can do
}
}
}
catch(Exception e) {
display("Exception closing the server and clients: " + e);
}
}
// something went bad
catch (IOException e) {
            String msg = sdf.format(new Date()) + " Exception on new ServerSocket: " + e + "\n";
display(msg);
}
}
    /*
     * For the GUI to stop the server
     */
protected void stop() {
keepGoing = false;
// connect to myself as Client to exit statement
// Socket socket = serverSocket.accept();
try {
new Socket("localhost", port);
}
catch(Exception e) {
// nothing I can really do
}
}
/*
* Display an event (not a message) to the console or the GUI
*/
private void display(String msg) {
String time = sdf.format(new Date()) + " " + msg;
if(sg == null)
System.out.println(time);
else
sg.appendEvent(time + "\n");
}
/*
* to broadcast a message to all Clients
*/
private synchronized void broadcast(String message) {
// add HH:mm:ss and \n to the message
String time = sdf.format(new Date());
String messageLf = time + " " + message + "\n";
// display message on console or GUI
if(sg == null)
System.out.print(messageLf);
else
sg.appendRoom(messageLf);     // append in the room window

// we loop in reverse order in case we would have to remove a Client
// because it has disconnected
for(int i = al.size(); --i >= 0;) {
ClientThread ct = al.get(i);
// try to write to the Client if it fails remove it from the list
if(!ct.writeMsg(messageLf)) {
al.remove(i);
display("Disconnected Client " + ct.username + " removed from list.");
}
}
}

// for a client who logoff using the LOGOUT message
synchronized void remove(int id) {
// scan the array list until we found the Id
for(int i = 0; i < al.size(); ++i) {
ClientThread ct = al.get(i);
// found it
if(Page on ct.id == id) {
al.remove(i);
return;
}
}
}

/*
* To run as a console application just open a console window and:
* > java Server
* > java Server portNumber
* If the port number is not specified 1500 is used
*/
public static void main(String[] args) {
// start server on port 1500 unless a PortNumber is specified
int portNumber = 1500;
switch(args.length) {
case 1:
try {
portNumber = Integer.parseInt(args[0]);
}
catch(Exception e) {
System.out.println("Invalid port number.");
System.out.println("Usage is: > java Server [portNumber]");
return;
}
case 0:
break;
default:
System.out.println("Usage is: > java Server [portNumber]");
return;

}
// create a server object and start it
Server server = new Server(portNumber);
server.start();
}

/** One instance of this thread will run for each client */
class ClientThread extends Thread {
// the socket where to listen/talk
Socket socket;
ObjectInputStream sInput;
ObjectOutputStream sOutput;
// my unique id (easier for deconnection)
int id;
// the Username of the Client
String username;
// the only type of message a will receive
ChatMessage cm;
// the date I connect
String date;

// Constructore
ClientThread(Socket socket) {
// a unique id
id = ++uniqueId;
this.socket = socket;
/* Creating both Data Stream */
System.out.println("Thread trying to create Object Input/Output Streams");
try
{
// create output first
sOutput = new ObjectOutputStream(socket.getOutputStream());
sInput = new ObjectInputStream(socket.getInputStream());
// read the username
username = (String) sInput.readObject();
display(username + " just connected.");
}
catch (IOException e) {
display("Exception creating new Input/output Streams: " + e);
return;
}
// have to catch ClassNotFoundException
// but I read a String, I am sure it will work
catch (ClassNotFoundException e) {
}
            date = new Date().toString() + "\n";
}

// what will run forever
public void run() {
// to loop until LOGOUT
boolean keepGoing = true;
while(keepGoing) {
// read a String (which is an object)
try {
cm = (ChatMessage) sInput.readObject();
}
catch (IOException e) {
display(username + " Exception reading Streams: " + e);
break;
}
catch(ClassNotFoundException e2) {
break;
}
// the messaage part of the ChatMessage
String message = cm.getMessage();

// Switch on the type of message receive
switch(cm.getType()) {

case ChatMessage.MESSAGE:
broadcast(username + ": " + message);
break;
case ChatMessage.LOGOUT:
display(username + " disconnected with a LOGOUT message.");
keepGoing = false;
break;
case ChatMessage.WHOISIN:
writeMsg("List of the users connected at " + sdf.format(new Date()) + "\n");
// scan al the users connected
for(int i = 0; i < al.size(); ++i) {
ClientThread ct = al.get(i);
writeMsg((i+1) + ") " + ct.username + " since " + ct.date);
}
break;
}
}
// remove myself from the arrayList containing the list of the
// connected Clients
remove(id);
close();
}

// try to close everything
private void close() {
// try to close the connection
try {
if(sOutput != null) sOutput.close();
}
catch(Exception e) {}
try {
if(sInput != null) sInput.close();
}
catch(Exception e) {};
try {
if(socket != null) socket.close();
}
catch (Exception e) {}
}

/*
* Write a String to the Client output stream
*/
private boolean writeMsg(String msg) {
// if Client is still connected send the message to it
if(!socket.isConnected()) {
close();
return false;
}
// write the message to the stream
try {
sOutput.writeObject(msg);
}
// if an error occurs, do not abort just inform the user
catch(IOException e) {
display("Error sending message to " + username);
display(e.toString());
}
return true;
}
}
}