Java user Defined Exception Handling - Hello Exception

/*

Write a java program for exception handling:

To create a user defined exception whenever user input the word "hello".

*/

// java Exception Handling

// user defined exception

import java.util.*;

class userdefinedexception extends Exception

{

     public String toString()

     {

          return ("Hello Exception");

     }

}

class UsrDefException

{

     public static void main(String args[])

     {

          String str;

          Scanner s = new Scanner(System.in);

          try

          {

              System.out.print("Enter name : ");

              str = s.next().trim();

             

              // throw is used to create a new exception and throw it.

              if(str.equalsIgnoreCase("HELLO"))

              {

                   throw new userdefinedexception();

              }

              else

                   System.out.print("Hello "+str);

          }

          catch(userdefinedexception e)

          {

              System.out.println(e) ;

          }

     }

}

/*

Sample output

D:\oopjava>javac UsrDefException.java

D:\oopjava>java UsrDefException

Enter name : asdf

Hello asdf

D:\oopjava>java UsrDefException

Enter name : hello

Hello Exception

D:\oopjava>

*/

TCP/IP SOCKET APPLICATION - BROADCASTING

TCP/IP SOCKET APPLICATION

// BROADCAST 

// SERVER PROGRAM

import java.io.*;

import java.net.*;

class sock

{

     Socket s[] = new Socket[20];

     int cnt=0;

}

class cthd extends Thread

{

     Socket s1;

     String str;

     BufferedReader in;

     PrintWriter out;

     int cnt;

     sock so;

     cthd( sock p1, int i)

     {

          s1 = p1.s[i];

          cnt=i;

          so=p1;

          start();

     }

     public void run()

     {

          try

          {

              in = new BufferedReader(new InputStreamReader(s1.getInputStream()));

              for(int l=0;l<cnt;l++)

              {

                   out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(so.s[l].getOutputStream())),true);

                   out.println("the client number " +cnt+" has logged in");

              }

              while(true)

              {

                   str=in.readLine();

         

                   for(int i=0; i<so.cnt;i++)

                   {

                        out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(so.s[i].getOutputStream())),true);

                        if(str.equalsIgnoreCase("exit"))

                        {

                             if(i==cnt)

                                  out.println(str);

                             else

                                  out.println("Client number " +cnt+ ":"+str+"\n"+" the client  number"+cnt+"has logged out");

                        }

                        else

                             out.println("Client number" +cnt+":"+str);

                   }

              }

          }

          catch(Exception e)

          {  

          }

     }

}

public class BroadcastServer

{

     public static void main(String a[]) throws Exception

     {

          ServerSocket ss = new ServerSocket(3000);

          sock so = new sock();

          while(true)

          {

              so.s[so.cnt] = ss.accept();

              new cthd(so,so.cnt++);

          }

     }

}

// BROADCAST

// CLIENT PROGRAM

import java.io.*;

import java.net.*;

class Reader extends Thread

{

     Socket s;

     public Reader(Socket s1)

     {

          s = s1;

          start();

     }

     public void run()

     {

          try

          {

              BufferedReader i = new BufferedReader(new InputStreamReader(s.getInputStream()));

              while(true)

              {

                   String str = i.readLine();

                   System.out.println(str);

              }

          }

          catch(Exception e)

          {

          }

     }

}

class Writer extends Thread

{

     Socket s;

     public Writer(Socket s1)

     {

          s = s1;

          start();

     }

   public void run()

   {

          try

          {

              PrintWriter o = new PrintWriter(new BufferedWriter(new OutputStreamWriter(s.getOutputStream())),true);

              BufferedReader i = new BufferedReader(new InputStreamReader(System.in));

              while(true)

              {

                   String str = i.readLine();

                   o.println(str);

                   if(str.equalsIgnoreCase("exit"))

                   {

                        s.close();

                        break;

                   }

               }

          }

          catch(Exception e)

          {

          }

         

    }

}

class BroadcastClient

{

     public static void main(String a[]) throws Exception

     {

          try

          {

              Socket s;

              s = new Socket(InetAddress.getLocalHost(),3000);

             

              new Reader(s);

              new Writer(s);

          }

          catch(Exception e)

          {

          }

     }

}

/*

Execution.

First compile and execute the server.

Open 2 or more client windows and connect to the server.

When a client connects to the server, the server informs all the other connected clients about the new login.

When a client sends messages, the server broadcasts to all client windows.

Type 'exit' to terminate the client window.

*/