This is a homework assignment I am having trouble with.
I need to make an integer to Roman Numeral converter using a method. Later, I must then use the program to write out 1 to 3999 in Roman numerals, so hardcoding is out. My code below is very bare-bones; it is a basic I/O loop with a way to exit while using a package for getIntegerFromUser
we made in class.
Is there a way to assign values to Strings and then add them together when I call the method?
Update: I got some pseudo code from my professor to help me, and while I understand what he is trying to say, I am having some trouble with the if
s. Will I be needing many, many if
statements so that my converter will correctly handle the Roman numeral formatting or is there a manner in which I can do this with more efficiency? I've updated my code to reflect my placeholder method.
Update (Oct 28 2012): I got it working. Here's what I ended up using:
public static String IntegerToRomanNumeral(int input) {
if (input < 1 || input > 3999)
return "Invalid Roman Number Value";
String s = "";
while (input >= 1000) {
s += "M";
input -= 1000; }
while (input >= 900) {
s += "CM";
input -= 900;
}
while (input >= 500) {
s += "D";
input -= 500;
}
while (input >= 400) {
s += "CD";
input -= 400;
}
while (input >= 100) {
s += "C";
input -= 100;
}
while (input >= 90) {
s += "XC";
input -= 90;
}
while (input >= 50) {
s += "L";
input -= 50;
}
while (input >= 40) {
s += "XL";
input -= 40;
}
while (input >= 10) {
s += "X";
input -= 10;
}
while (input >= 9) {
s += "IX";
input -= 9;
}
while (input >= 5) {
s += "V";
input -= 5;
}
while (input >= 4) {
s += "IV";
input -= 4;
}
while (input >= 1) {
s += "I";
input -= 1;
}
return s;
}
A compact implementation using Java TreeMap and recursion:
import java.util.TreeMap;
public class RomanNumber {
private final static TreeMap<Integer, String> map = new TreeMap<Integer, String>();
static {
map.put(1000, "M");
map.put(900, "CM");
map.put(500, "D");
map.put(400, "CD");
map.put(100, "C");
map.put(90, "XC");
map.put(50, "L");
map.put(40, "XL");
map.put(10, "X");
map.put(9, "IX");
map.put(5, "V");
map.put(4, "IV");
map.put(1, "I");
}
public final static String toRoman(int number) {
int l = map.floorKey(number);
if ( number == l ) {
return map.get(number);
}
return map.get(l) + toRoman(number-l);
}
}
Testing:
public void testRomanConversion() {
for (int i = 1; i<= 100; i++) {
System.out.println(i+"\t =\t "+RomanNumber.toRoman(i));
}
}