Convert Roman numerals to decimal using Java

 Posted by Samath   22665 December 21, 2014

Write a program that converts a number entered in Roman numerals to decimal. Your program should consist of a class, say, Roman. An object of type Roman should do the following:

a. Store the number as a Roman numeral.

b. Convert and store the number into decimal.

c. Print the number as a Roman numeral or decimal number as requested by the user.

The decimal values of the Roman numerals are:
M 1000
D 500
C 100
L 50
X 10
V 5
I 1

d. You should be able to enter data into your program using the following Roman numerals : MCXIV, CCCLIX, and MDCLXVI which should be able to produce outputs as shown below

Enter a roman number: MCXIV
The equivalent of the Roman numeral MCXIV is 1114

Enter a roman number: CCCLIX
The equivalent of the Roman numeral CCCLIX is 359

Enter a roman number: MDCLXVI
The equivalent of the Roman numeral MDCLXVI is 1666

Solution:

```import java.util.Scanner;

public class Roman {
static String romanNumeral;
static int decimalNum;
public static void main(String args[]) {
Roman rmtoD = new Roman();
rmtoD .convertToDecimal();
rmtoD .printRoman(romanNumeral);
}

public void convertToDecimal () {
Scanner scan = new Scanner(System.in);
System.out.print("Enter a Roman number: ");
romanNumeral = scan.nextLine();
romanNumeral = romanNumeral.toUpperCase();

int l=  romanNumeral.length();
int num=0;
int previousnum = 0;
for (int i=l-1;i>=0;i--)
{
char x =  romanNumeral.charAt(i);
x = Character.toUpperCase(x);
switch(x)
{
case 'I':
previousnum = num;
num = 1;
break;
case 'V':
previousnum = num;
num = 5;
break;
case 'X':
previousnum = num;
num = 10;
break;
case 'L':
previousnum = num;
num = 50;
break;
case 'C':
previousnum = num;
num = 100;
break;
case 'D':
previousnum = num;
num = 500;
break;
case 'M':
previousnum = num;
num = 1000;
break;
}
if (num<previousnum)
{decimalNum= decimalNum-num;}
else
decimalNum= decimalNum+num;
}
}
public static void printRoman (String romanNumeral){
System.out.println ("The equivalent of the Roman numeral "+romanNumeral+" is "+decimalNum);
}

public static void printDecimal (int decimalNum){
System.out.println ("Decimal Number stored is: " + decimalNum);
}

}```