Hexa.java

public class Main {

    public static void main( String[] args ) {
        System.out.println( getHexa( 255 ) );
    }
    
    private static String getHexa( int i ) {
        int r = i % 16;
        String s = "";
        switch ( r ) {
            case 0:
                s += "0";
                break;
            case 1:
                s += "1";
                break;
            case 2:
                s += "2";
                break;
            case 3:
                s += "3";
                break;
            case 4:
                s += "4";
                break;
            case 5:
                s += "5";
                break;
            case 6:
                s += "6";
                break;
            case 7:
                s += "7";
                break;
            case 8:
                s += "8";
                break;
            case 9:
                s += "9";
                break;
            case 10:
                s += "A";
                break;
            case 11:
                s += "B";
                break;
            case 12:
                s += "C";
                break;
            case 13:
                s += "D";
                break;
            case 14:
                s += "E";
                break;
            case 15:
                s += "F";
                break;
        }
        return ( i - r != 0 ? getHexa( i / 16 ) : "" ) + s;
    }
    
}