# Roman Numeral To Decimal in Java

Nov 19, 2021

A simple program to ask the user to give roman numeral and then the program will convert the given roman numeral into decimal equivalent using Java programming language.

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Program Listing

``````import java.util.*;
import java.util.Scanner;

class Roman_To_Decimal
{

public static int romanToInteger(String roman)
{
Map<Character,Integer> numbersMap = new HashMap<>();
numbersMap.put('I',1);
numbersMap.put('V',5);
numbersMap.put('X',10);
numbersMap.put('L',50);
numbersMap.put('C',100);
numbersMap.put('D',500);
numbersMap.put('M',1000);

int result=0;

for(int i=0;i<roman.length();i++)
{
char ch = roman.charAt(i);      // Current Roman Character

//Case 1
if(i>0 && numbersMap.get(ch) > numbersMap.get(roman.charAt(i-1)))
{
result += numbersMap.get(ch) - 2*numbersMap.get(roman.charAt(i-1));
}

// Case 2: just add the corresponding number to result.
else
result += numbersMap.get(ch);
}

return result;
}

public static void main(String args[])
{

Scanner input = new Scanner(System.in);  // Create a Scanner object

System.out.println("\n");
System.out.print("\t\tRoman Numeral To Decimal in Java");
System.out.println("\n");
System.out.print("\tGive Roman Numberal Value : ");

String romanNumber = input.nextLine();

int result = romanToInteger(romanNumber.toUpperCase());

System.out.println();
System.out.println("\tThe Roman Number is: "+romanNumber.toUpperCase());
System.out.println();
System.out.println("\tIts Decimal Value is: "+result);

System.out.println();
System.out.println("\tEnd of Program");
System.out.println();
input.close();
}
}
``````