Convert Binary to Hexadecimal source code in java

كود:

---

import java.io.*;
import java.lang.*;

public class  BinaryToHexa{
public static void main(String[] args)throws IOException{
BufferedReader bf= new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the Binary number:");
String hex = bf.readLine();
long num = Long.parseLong(hex);
long rem;
while(num > 0){
rem = num % 10;
num = num / 10;
if(rem != 0 && rem != 1){
System.out.println("This is not a binary number.");
System.out.println("Please try once again.");
System.exit(0);
}
}
int i= Integer.parseInt(hex,2);
String hexString = Integer.toHexString(i);
System.out.println("Hexa decimal: " + hexString);
}
}

---