Crc.java

import java.io.*;
import java.net.*;
class Crc
{
	public static void main(String args[]) throws IOException
	{
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		System.out.println("\nEnter Generator: ");
		String gen=br.readLine();
		System.out.println("\nEnter data: ");
		String data=br.readLine();
		String code=data;
		while(code.length()<(data.length()+gen.length()-1))
		code=code+"0";
		code=data+div(code,gen);
		System.out.println("\nThe transmitted code word is: "+code);
		System.out.println("\nPlease enter the received code word: ");
		String rec=br.readLine();
		if(Integer.parseInt(div(rec, gen))==0)
		System.out.println("\nThe received code word contains NO Errors.\n");
		else
		System.out.println("\nThe received code word contains Errors.\n");
	}
	static String div(String num1, String num2)
	{
		int pointer=num2.length();
		String result=num1.substring(0, pointer);
		String remainder="";
		for (int i=0; i<num2.length(); i++)
		{
			if (result.charAt(i)==num2.charAt(i))
			remainder+="0";
			else
			remainder+="1";
		}
		while(pointer<num1.length())
		{
			if(remainder.charAt(0)=='0')
			{
				remainder=remainder.substring(1, remainder.length());
				remainder=remainder+String.valueOf(num1.charAt(pointer));
				pointer++;
			}
			result=remainder;
			remainder="";
			for(int i=0; i<num2.length(); i++)
			{
				if (result.charAt(i)==num2.charAt(i))
				remainder+="0";
				else
				remainder+="1";
			}
		}
		return remainder.substring(1, remainder.length());
	}
}