Cyclic Redundancy Code

Cyclic Redundancy Code import java.util.*;


class U
{
public  static String remainder(String data, String divisor) {
    int x = 1, z = divisor.length(), j = 0, i;
    String data2 = "", strOfZeros = "";
    int y = divisor.length() - 1;
    /* This is to get correct amount of zero's onto the end of the data */
    while (y > 0) {
        data += "0";
        y--;
    }
    // Main part of method, this is the long division of Binary numbers.
    needToExit: for (i = x, j = 1; i < z && z <= data.length(); i++, j++) {
        if (z == data.length() && data2.charAt(0) == '1') {
            strOfZeros = "";
            for (i = 1; i < divisor.length(); i++) {   
                if (data2.charAt(i) == divisor.charAt(i))
                    strOfZeros += '0';
                else
                    strOfZeros += '1';
            }
            data2 = strOfZeros;
            break needToExit;
        }

        if (data.charAt(i) == divisor.charAt(j))
            data2 += "0";
        else
            data2 += "1";

        if (i == divisor.length() - 1) {
            data2 += data.charAt(z);
            x++;
            z++;
            // i = x;
            j = 0;

            // when first bit is a 0
            while (data2.charAt(0) != '1' && i == divisor.length() - 1) {
                for (i = 1; i < divisor.length(); i++) {
                    if (data2.charAt(i) == '0')
                        strOfZeros += "0";
                    else
                        strOfZeros += "1";
                }
                strOfZeros += data.charAt(z);
                data2 = strOfZeros;
                strOfZeros = "";
                x++;
                z++;
                i = x;
            }
        }

    }
    return data2;
}
public static String codeword(String x,String y)
{
StringBuffer d=new StringBuffer(x);
for(int i=0;i<y.length();i++)
{
char c,l;
c=d.charAt(d.length()-i-1);
l=y.charAt(y.length()-i-1);
int a=(int)c-48;
int b=(int)c-48;
int q=a^b;
d.setCharAt((d.length()-i-1),(char)(q+48));
}
String h=d.toString();
return h;
}
}
class CRCC
{
public static void main(String args[])
{
Scanner src=new Scanner(System.in);
System.out.println("enter the data word");
String s=src.nextLine();
System.out.println("enter the divisor");
String x=src.nextLine();
String h=U.remainder(s,x);
System.out.println("the remainder is:"+h);
String a=U.codeword(s,h);
System.out.println("the codewordis:"+a);
Random r=new Random();
String w="";
StringBuffer sb=new StringBuffer(w);
for(int i=0;i<7;i++);
{
if(r.nextBoolean()==true)
sb.append('1');
else
sb.append('0');
}
System.out.println("the recieved bits are:"+sb);
String j=sb.toString();
String k=U.remainder(j,x);
if(k=="000")
System.out.println("No ERROR");
else
System.out.println("ERROR");
}
}