To find class, subnet mask, first and last IP of the block in which given IP is present

/* To find class, subnet mask, first and last IP of the block in which given IP is present */

import java.io.*;

class Ipfind

{

                public static void main(String[] args)throws IOException {

                               

                                DataInputStream dis = new DataInputStream(System.in);

                                System.out.println("Enter IP Address (eg: 192.168.1.1)");

                                String ipAddr = dis.readLine();

                                String[] ipAddrParts=ipAddr.split("\\.");

                                String mask="";

                                int firstoctet = Integer.parseInt(ipAddrParts[0]);

                                if(firstoctet<=127)

                                {

                                                mask = "255.0.0.0";

                                                System.out.println("Class A IP Address");

                                                System.out.println("The Subnet mask is: "+mask);

                                }

                                else if(firstoctet>=128 && firstoctet<=191)

                                {

                                                mask = "255.255.0.0";

                                                System.out.println("Class B IP Address");

                                                System.out.println("The Subnet mask is: "+mask);

                                }

                                else if(firstoctet>=192 && firstoctet<=223)

                                {

                                                mask = "255.255.255.0";

                                                System.out.println("Class C IP Address");

                                                System.out.println("The Subnet mask is: "+mask);

                                }

                                else if(firstoctet>=224 && firstoctet<=239)

                                {

                                                mask = "255.0.0.0";

                                                System.out.println("Class D IP Address; Used for multicasting");

                                }

                                else if(firstoctet>=240 && firstoctet<=254)

                                {

                                                mask = "255.0.0.0";

                                                System.out.println("Class D IP Address; Experimental Use");

                                }

                               

                                String[] maskParts=mask.split("\\.");

                                String firstAddr="";

                                String lastAddr="";

                                for(int i=0;i<4;i++){

                int x=Integer.parseInt(ipAddrParts[i]);

                int y=Integer.parseInt(maskParts[i]);

                int z=x&y;

                int w=z|(y^255);               //last ip = ipaddress && subnetmask + ~subnetmask

                firstAddr+=z+".";

                lastAddr+=w+".";

            }

        System.out.println("First IP of block: "+firstAddr);

        System.out.println("Last IP of block: "+lastAddr);

                }

}

OUTPUT:

C:\Documents and Settings\students\My Documents\Downloads>java Ipfind

Enter IP Address (eg: 192.168.1.1)

10.0.6.162

Class A IP Address

The Subnet mask is: 255.0.0.0

First IP of block: 10.0.0.0.

Last IP of block: 10.255.255.255.