Cyclic Redundancy Check (CRC) - Java | Computer Networks

import java.io.*;

public class crc_gen 

{

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

    {

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

        int[] data;

        int[] div;

        int[] divisor;

        int[] rem;

        int[] crc;

        int data_bits, divisor_bits, tot_length;      

        System.out.println("Enter number of data bits : ");

        data_bits=Integer.parseInt(br.readLine());

        data=new int[data_bits];

        System.out.println("Enter data bits : ");

        for(int i=0; i<data_bits; i++)

            data[i]=Integer.parseInt(br.readLine());

        System.out.println("Enter number of bits in divisor : ");

        divisor_bits=Integer.parseInt(br.readLine());

        divisor=new int[divisor_bits];     

        System.out.println("Enter Divisor bits : ");

        for(int i=0; i<divisor_bits; i++)

            divisor[i]=Integer.parseInt(br.readLine());

        System.out.print("Data bits are : ");

        for(int i=0; i< data_bits; i++)

            System.out.print(data[i]);       

        System.out.println();

        System.out.print("divisor bits are : ");

        for(int i=0; i< divisor_bits; i++)

            System.out.print(divisor[i]);       

        System.out.println();

             tot_length=data_bits+divisor_bits-1;     

        div=new int[tot_length];

        rem=new int[tot_length];

        crc=new int[tot_length];

        for(int i=0;i<data.length;i++)

            div[i]=data[i];

        System.out.print("Dividend (after appending 0's) are : ");

        for(int i=0; i< div.length; i++)

            System.out.print(div[i]);       

        System.out.println();  

        for(int j=0; j<div.length; j++){

              rem[j] = div[j];

        }

            rem=divide(div, divisor, rem);

                for(int i=0;i<div.length;i++)                  {

            crc[i]=(div[i]^rem[i]);

        }

        System.out.println();

        System.out.println("CRC code : ");   

        for(int i=0;i<crc.length;i++)

            System.out.print(crc[i]);

        System.out.println();

        System.out.println("Enter CRC code of "+tot_length+" bits : ");

        for(int i=0; i<crc.length; i++)

            crc[i]=Integer.parseInt(br.readLine());

         System.out.print("CRC bits are : ");

        for(int i=0; i< crc.length; i++)

            System.out.print(crc[i]);       

        System.out.println();     

        for(int j=0; j<crc.length; j++){

              rem[j] = crc[j];

        } 

        rem=divide(crc, divisor, rem);

        for(int i=0; i< rem.length; i++)

        {

            if(rem[i]!=0)

            {

                System.out.println("Error");

                break;

            }

            if(i==rem.length-1)

                System.out.println("No Error");

        }

    }

      static int[] divide(int div[],int divisor[], int rem[])

    {

        int cur=0;

        while(true)

        {

            for(int i=0;i<divisor.length;i++)

                rem[cur+i]=(rem[cur+i]^divisor[i]);    

            while(rem[cur]==0 && cur!=rem.length-1)

                cur++;

               if((rem.length-cur)<divisor.length)

                break;

        }

        return rem;

    }

}