Check this link.
http://www.roseindia.net/java/java-conversion/DecimalToHexadecimal.shtml

Hi Friend,

Try the following code:

import java.util.*;
public class RomanToDecimal {
public static void main(String args[]) {
int decimal=0;
Scanner input=new Scanner(System.in);
System.out.println("Enter a Roman Number: ");
String roman = input.next();
String romanNumeral = roman.toUpperCase();
int x = 0;
do{
char convertToDecimal = roman.charAt(x);
switch(convertToDecimal){
case 'M':
decimal += 1000;
break;

case 'D':
decimal += 500;
break;

case 'C':
decimal += 100;
break;

case 'L':
decimal += 50;
break;

case 'X':
decimal += 10;
break;

case 'V':
decimal += 5;
break;

case 'I':
decimal += 1;
break;
}
x++;
}while(x<romanNumeral.length());
System.out.println("Decimal Number is: " + decimal);
}
}

Thanks