Code in Java Write a program to implement the checksum method. The implementatio

Question

Code in Java

Write a program to implement the checksum method.

The implementation has two parts:

1. Calculating the checksum at the sender

Inputs: 4 data each consisting of 16-bit (binary)

Output: Checksum of 16-bit (binary)

Example: http://mathforum.org/library/drmath/view/54379.html

2. Verifying the checksum at the receiver

Inputs: 4 data each is consisting of 16-bit and their 16-bit checksum

Output: Checksum for 4 data each is consisting of 16-bit and their 16-bit checksum

If checksum is equal to 0s, your data is not corrupted

If checksum is not equal 0s, your data is corrupted

Explanation / Answer

Hi.

Please see below the classes .Pleasecomment foranu queries.

Thanks.

Sender.java

public class Sender {
   public int generateChecksum(String s)
   {
   String hex_value = new String();
   // 'hex_value' will be used to store various hex values as a string
   int x, i, checksum = 0;
   // 'x' will be used for general purpose storage of integer values
   // 'i' is used for loops
   // 'checksum' will store the final checksum
   for (i = 0; i < s.length() - 2; i = i + 2)
   {
   x = (int) (s.charAt(i));
   hex_value = Integer.toHexString(x);
   x = (int) (s.charAt(i + 1));
   hex_value = hex_value + Integer.toHexString(x);
   // Extract two characters and get their hexadecimal ASCII values
   System.out.println(s.charAt(i) + "" + s.charAt(i + 1) + " : "
   + hex_value);
   x = Integer.parseInt(hex_value, 16);
   // Convert the hex_value into int and store it
   checksum += x;
   // Add 'x' into 'checksum'
   }
   if (s.length() % 2 == 0)
   {
   // If number of characters is even, then repeat above loop's steps
   // one more time.
   x = (int) (s.charAt(i));
   hex_value = Integer.toHexString(x);
   x = (int) (s.charAt(i + 1));
   hex_value = hex_value + Integer.toHexString(x);
   System.out.println(s.charAt(i) + "" + s.charAt(i + 1) + " : "
   + hex_value);
   x = Integer.parseInt(hex_value, 16);
   }
   else
   {
   // If number of characters is odd, last 2 digits will be 00.
   x = (int) (s.charAt(i));
   hex_value = "00" + Integer.toHexString(x);
   x = Integer.parseInt(hex_value, 16);
   System.out.println(s.charAt(i) + " : " + hex_value);
   }
   checksum += x;
   // Add the generated value of 'x' from the if-else case into 'checksum'
   hex_value = Integer.toHexString(checksum);
   // Convert into hexadecimal string
   if (hex_value.length() > 4)
   {
   // If a carry is generated, then we wrap the carry
   int carry = Integer.parseInt(("" + hex_value.charAt(0)), 16);
   // Get the value of the carry bit
   hex_value = hex_value.substring(1, 5);
   // Remove it from the string
   checksum = Integer.parseInt(hex_value, 16);
   // Convert it into an int
   checksum += carry;
   // Add it to the checksum
   }
   checksum = generateComplement(checksum);
   // Get the complement
   return checksum;
   }
     
   /**
       * generateComplement
       * @param checksum
       * @return
       */
       public int generateComplement(int checksum)
       {
           // Generates 15's complement of a hexadecimal value
           checksum = Integer.parseInt("FFFF", 16) - checksum;
           return checksum;
       }
}

Receiver.java

public class Receiver {
   /**
   * receive
   * @param s
   * @param checksum
   */
   public void receive(String s, int checksum)
   {
       Sender sender = new Sender();
       int generated_checksum = sender.generateChecksum(s);
       // Calculate checksum of received data
       generated_checksum = generateComplement(generated_checksum);
       // Then get its complement, since generated checksum is complemented
       int syndrome = generated_checksum + checksum;
       // Syndrome is addition of the 2 checksums
       syndrome = generateComplement(syndrome);
       // It is complemented
       System.out.println("Syndrome = " + Integer.toHexString(syndrome));
       if (syndrome == 0)
       {
           System.out.println("Data is received without error.");
       }
       else
       {
           System.out.println("There is an error in the received data.");
       }
   }

   /**
   * generateComplement
   * @param checksum
   * @return
   */
   public int generateComplement(int checksum)
   {
       // Generates 15's complement of a hexadecimal value
       checksum = Integer.parseInt("FFFF", 16) - checksum;
       return checksum;
   }
}

ChecksumDemo.java

import java.util.*;

public class ChecksumDemo
{
public static void main(String args[])
{
Scanner scan = new Scanner(System.in);
System.out.println("Enter the string input:");
String input = scan.next();
Sender sender = new Sender();
Receiver reveiver = new Receiver();
int checksum = sender.generateChecksum(input);
// Call the method to create the checksum
System.out.println("The checksum generated is = "
+ Integer.toHexString(checksum));
System.out.println("Enter the data to be sent:");
input = scan.next();
System.out.println("Enter the checksum to be sent:");
checksum = Integer.parseInt((scan.next()), 16);
// User inputs data as hexadecimal value but it will be stored as a
// decimal value unless it is converted into hexadecimal first.
reveiver.receive(input, checksum);
scan.close();
}




}

Sample output:

Enter the string input:
1101101110011000
11 : 3131
01 : 3031
10 : 3130
11 : 3131
10 : 3130
01 : 3031
10 : 3130
00 : 3030
The checksum generated is = 797a
Enter the data to be sent:
1101101110011000
Enter the checksum to be sent:
797a
11 : 3131
01 : 3031
10 : 3130
11 : 3131
10 : 3130
01 : 3031
10 : 3130
00 : 3030
Syndrome = 0
Data is received without error.

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