Introduction

In this demo I have used NetBeans IDE 8.2 for debugging purpose. But you can use any java programming language compiler as per your availability..

public class Javamathexcercise {
   public static void main(String[] args) {
 
    String str = "XXVIVI";
    int len = str.length();
 
        str = str + " ";
        int result = 0;
        for (int i = 0; i < len; i++) {
            char ch   = str.charAt(i);
            char next_char = str.charAt(i+1);
 
            if (ch == 'M') {
                result += 1000;
            } else if (ch == 'C') {
                if (next_char == 'M') {
                    result += 900;
                    i++;
                } else if (next_char == 'D') {
                    result += 400;
                    i++;
                } else {
                    result += 100;
                }
            } else if (ch == 'D') {
                result += 500;
            } else if (ch == 'X') {
                if (next_char == 'C') {
                    result += 90;
                    i++;
                } else if (next_char == 'L') {
                    result += 40;
                    i++;
                } else {
                    result += 10;
                }
            } else if (ch == 'L') {
                result += 50;
            } else if (ch == 'I') {
                if (next_char == 'X') {
                    result += 9;
                    i++;
                } else if (next_char == 'V') {
                    result += 4;
                    i++;
                } else {
                    result++;
                }
            } else { // if (ch == 'V')
                result += 5;
            }
        }
       System.out.println("\nRoman Number: "+str);
       System.out.println("Equivalent Integer: "+result+"\n");
    }
}

Result