Programming Assignment 5 Java Keyword Identifier Note: When you turn in an assig

ID: 3813109 • Letter: P

Question

Programming Assignment 5 Java Keyword Identifier Note: When you turn in an assignment to be graded in this class, you are making the claim that you neither gave nor received assistance on the work you turned in (except, of course, assistance from the instructor) Project Description Variables in a computer program are programmer-defined and serve as a named location in memory Selecting good identifiers helps with the human understanding and maintainability of source code. But there are restrictions imposed on identifiers by the Java language. These rules and conventions are summarized here Variable names are case-sensitive. A variable's name can be any legal identifier an unlimited-length sequence of Unicode letters and digits, beginning with a letter, the dollar sign "S", or the underscore character The convention, however, is to always begin your variable names with a letter, not or ditionally, the dollar sign character, by convention, is never used at all. You may find some situations where auto-generated names will contain the dollar sign, but your variable names should always avoid using it. A similar convention exists for the underscore character; while it's technically legal to begin your variable's name with this practice is discouraged. White space is not permitted Subsequent characters may be letters, digits, dollar signs, or underscore characters Conventions (and common sense) apply to this rule as well. When choosing a name for your variables, use full words instead of cryptic abbreviations. Doing so will make your code easier to read and understand. In many cases it will also make your code self-documenting; fields named cadence, speed, and gear, for example, are much more intuitive than abbreviated versions, such as s, c, and g. Also keep in mind that the name you choose must not be a keyword or reserved word If the name you choose consists of only one word, spell that word in a lowercase letters. If it consists of more than one word, capitalize the first letter of each subsequent word. The names gearRatio and currentGear are prime examples of this convention. If your variable stores a constant value, such as static final int NUM GEARS 6, the convention changes slightly, capitalizing every letter and separating subsequent words with the underscore character. By convention, the underscore character is never used elsewhere. (Oracle.com, 2015)

Explanation / Answer

import java.io.*;
import java.net.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/*************************/
class MyServer
{
ArrayList al=new ArrayList();
ArrayList users=new ArrayList();
ServerSocket ss;
Socket s;

public final static int PORT=10;
public final static String UPDATE_USERS="updateuserslist:";
public final static String LOGOUT_MESSAGE="@@logoutme@@:";
public MyServer()
{
try{
   ss=new ServerSocket(PORT);
   System.out.println("Server Started "+ss);
   while(true)
   {
   s=ss.accept();
   Runnable r=new MyThread(s,al,users);
   Thread t=new Thread(r);
   t.start();
//   System.out.println("Total alive clients : "+ss.);
   }
}
catch(Exception e){System.err.println("Server constructor"+e);}
}
/////////////////////////
public static void main(String [] args)
{
new MyServer();
}
/////////////////////////
}
/*************************/
class MyThread implements Runnable
{
Socket s;
ArrayList al;
ArrayList users;
String username;
///////////////////////
MyThread (Socket s, ArrayList al,ArrayList users)
{
this.s=s;
this.al=al;
this.users=users;
try{
   DataInputStream dis=new DataInputStream(s.getInputStream());
   username=dis.readUTF();
   al.add(s);
   users.add(username);
   tellEveryOne("****** "+ username+" Logged in at "+(new Date())+" ******");
   sendNewUserList();
}
catch(Exception e){System.err.println("MyThread constructor "+e);}
}
///////////////////////
public void run()
{
String s1;
try{
   DataInputStream dis=new DataInputStream(s.getInputStream());
   do
   {
   s1=dis.readUTF();
   if(s1.toLowerCase().equals(MyServer.LOGOUT_MESSAGE)) break;
//   System.out.println("received from "+s.getPort());
   tellEveryOne(username+" said: "+" : "+s1);
   }
   while(true);
   DataOutputStream tdos=new DataOutputStream(s.getOutputStream());
   tdos.writeUTF(MyServer.LOGOUT_MESSAGE);
   tdos.flush();
   users.remove(username);
   tellEveryOne("****** "+username+" Logged out at "+(new Date())+" ******");
   sendNewUserList();
   al.remove(s);
   s.close();

}
catch(Exception e){System.out.println("MyThread Run"+e);}
}
////////////////////////
public void sendNewUserList()
{
tellEveryOne(MyServer.UPDATE_USERS+users.toString());

}
////////////////////////
public void tellEveryOne(String s1)
{
Iterator i=al.iterator();
while(i.hasNext())
{
try{
   Socket temp=(Socket)i.next();
   DataOutputStream dos=new DataOutputStream(temp.getOutputStream());
   dos.writeUTF(s1);
   dos.flush();
   //System.out.println("sent to : "+temp.getPort()+" : "+ s1);
}
catch(Exception e){System.err.println("TellEveryOne "+e);}
}
}
///////////////////////
}
/*********************************/
class MyClient implements ActionListener
{
Socket s;
DataInputStream dis;
DataOutputStream dos;

JButton sendButton, logoutButton,loginButton, exitButton;
JFrame chatWindow;
JTextArea txtBroadcast;
JTextArea txtMessage;
JList usersList;

//////////////////////////
public void displayGUI()
{
chatWindow=new JFrame();
txtBroadcast=new JTextArea(5,30);
txtBroadcast.setEditable(false);
txtMessage=new JTextArea(2,20);
usersList=new JList();

sendButton=new JButton("Send");
logoutButton=new JButton("Log out");
loginButton=new JButton("Log in");
exitButton=new JButton("Exit");

JPanel center1=new JPanel();
center1.setLayout(new BorderLayout());
center1.add(new JLabel("Broad Cast messages from all online users",JLabel.CENTER),"North");
center1.add(new JScrollPane(txtBroadcast),"Center");

JPanel south1=new JPanel();
south1.setLayout(new FlowLayout());
south1.add(new JScrollPane(txtMessage));
south1.add(sendButton);

JPanel south2=new JPanel();
south2.setLayout(new FlowLayout());
south2.add(loginButton);
south2.add(logoutButton);
south2.add(exitButton);

JPanel south=new JPanel();
south.setLayout(new GridLayout(2,1));
south.add(south1);
south.add(south2);

JPanel east=new JPanel();
east.setLayout(new BorderLayout());
east.add(new JLabel("Online Users",JLabel.CENTER),"East");
east.add(new JScrollPane(usersList),"South");

chatWindow.add(east,"East");

chatWindow.add(center1,"Center");
chatWindow.add(south,"South");

chatWindow.pack();
chatWindow.setTitle("Login for Chat");
chatWindow.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
chatWindow.setVisible(true);
sendButton.addActionListener(this);
logoutButton.addActionListener(this);
loginButton.addActionListener(this);
exitButton.addActionListener(this);
logoutButton.setEnabled(false);
loginButton.setEnabled(true);
txtMessage.addFocusListener(new FocusAdapter()
{public void focusGained(FocusEvent fe){txtMessage.selectAll();}});

chatWindow.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent ev)
{
if(s!=null)
{
JOptionPane.showMessageDialog(chatWindow,"u r logged out right now. ","Exit",JOptionPane.INFORMATION_MESSAGE);
logoutSession();
}
System.exit(0);
}
});
}
///////////////////////////
public void actionPerformed(ActionEvent ev)
{
JButton temp=(JButton)ev.getSource();
if(temp==sendButton)
{
if(s==null)
    {JOptionPane.showMessageDialog(chatWindow,"u r not logged in. plz login first"); return;}
try{
   dos.writeUTF(txtMessage.getText());
   txtMessage.setText("");
}
catch(Exception excp){txtBroadcast.append(" send button click :"+excp);}
}
if(temp==loginButton)
{
String uname=JOptionPane.showInputDialog(chatWindow,"Enter Your lovely nick name: ");
if(uname!=null)
   clientChat(uname);
}
if(temp==logoutButton)
{
if(s!=null)
   logoutSession();
}
if(temp==exitButton)
{
if(s!=null)
{
JOptionPane.showMessageDialog(chatWindow,"u r logged out right now. ","Exit",JOptionPane.INFORMATION_MESSAGE);
logoutSession();
}
System.exit(0);
}
}
///////////////////////////
public void logoutSession()
{
if(s==null) return;
try{
dos.writeUTF(MyServer.LOGOUT_MESSAGE);
Thread.sleep(500);
s=null;
}
catch(Exception e){txtBroadcast.append(" inside logoutSession Method"+e);}

logoutButton.setEnabled(false);
loginButton.setEnabled(true);
chatWindow.setTitle("Login for Chat");
}
//////////////////////////
public void clientChat(String uname)
{
try{
s=new Socket(InetAddress.getLocalHost(),MyServer.PORT);
dis=new DataInputStream(s.getInputStream());
dos=new DataOutputStream(s.getOutputStream());
ClientThread ct=new ClientThread(dis,this);
Thread t1=new Thread(ct);
t1.start();
dos.writeUTF(uname);
chatWindow.setTitle(uname+" Chat Window");
}
catch(Exception e){txtBroadcast.append(" Client Constructor " +e);}
logoutButton.setEnabled(true);
loginButton.setEnabled(false);
}
///////////////////////////////
public MyClient()
{
displayGUI();
// clientChat();
}
///////////////////////////////
public static void main(String []args)
{
new MyClient();
}
//////////////////////////
}
/*********************************/
class ClientThread implements Runnable
{
DataInputStream dis;
MyClient client;

ClientThread(DataInputStream dis,MyClient client)
{
this.dis=dis;
this.client=client;
}
////////////////////////
public void run()
{
String s2="";
do
{
   try{
       s2=dis.readUTF();
       if(s2.startsWith(MyServer.UPDATE_USERS))
           updateUsersList(s2);
       else if(s2.equals(MyServer.LOGOUT_MESSAGE))
           break;
       else
           client.txtBroadcast.append(" "+s2);
       int lineOffset=client.txtBroadcast.getLineStartOffset(client.txtBroadcast.getLineCount()-1);
       client.txtBroadcast.setCaretPosition(lineOffset);
   }
   catch(Exception e){client.txtBroadcast.append(" ClientThread run : "+e);}
}
while(true);
}
//////////////////////////
public void updateUsersList(String ul)
{
Vector ulist=new Vector();

ul=ul.replace("[","");
ul=ul.replace("]","");
ul=ul.replace(MyServer.UPDATE_USERS,"");
StringTokenizer st=new StringTokenizer(ul,",");

while(st.hasMoreTokens())
{
String temp=st.nextToken();
ulist.add(temp);
}
client.usersList.setListData(ulist);
}
/////////////////////////
}
/*********************************/