Clear this to me, this binary thing. And the strange if clause.

Question

import java.util.Scanner;

//your code goes here
public class Converter {
public static String toBinaryString ( int n ) {
if ( n < 0 ) throw new IllegalArgumentException ( "n must be non-negative" );
// special case
if ( n == 0 ) return "0" ;
// build string from right to left
String s = "" ;
while ( n > 0 ) {
if ( n % 2 == 0 ) s = '0' + s ;
else s = '1' + s ;
n = n / 2 ;
}
return s ;
}
}

public class Program {
public static void main(String[ ] args) {
Scanner sc = new Scanner(System.in);
int x = sc.nextInt();
System.out.print(Converter.toBinaryString(x));
}
}