// Program: Convert from binary (decimal) to roman numerals.
//          This is the model without any user interface.
// Author : Fred Swartz
// Date   : 23 Jan 2006

package roman;

public class RomanConversion {
    
    // Parallel arrays used in the conversion process.
    private static final String[] RCODE = {"M", "CM", "D", "CD", "C", "XC", "L",
                                           "XL", "X", "IX", "V", "IV", "I"};
    private static final int[]    BVAL  = {1000, 900, 500, 400,  100,   90,  50,
                                           40,   10,    9,   5,   4,    1};
    
    //=========================================================== binaryToRoman
    public static String binaryToRoman(int binary) {
        if (binary <= 0 || binary >= 4000) {
            throw new NumberFormatException("Value outside roman numeral range.");
        }
        String roman = "";         // Roman notation will be accumualated here.
        
        // Loop from biggest value to smallest, successively subtracting,
        // from the binary value while adding to the roman representation.
        for (int i = 0; i < RCODE.length; i++) {
            while (binary >= BVAL[i]) {
                binary -= BVAL[i];
                roman  += RCODE[i];
            }
        }
        return roman;
    }  
}

    try {
        String dec = decimalTF.getText();
        int    bin = Integer.parseInt(dec);
        String rom = RomanConversion.binaryToRoman(bin);
        romanTF.setText(rom);
    } catch (NumberFormatException nfe) {
        romanTF.setText("Invalid input.");
    }