how to add roman numbers in java

Question

I am having trouble with a programming assignment for computer science class. The program is to add to roman numerals. I don't know how to get started with the code that actually adds the roman numbers together and outputs the sum of the two numbers: here is the code that i have so far for the main program:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

/**
 * Class RomanNumeralCalculator - write a description of the class here
 * 
 * @author (your name) 
 * @version (a version number)
*/
public class RomanNumeralCalculator extends JFrame
{
   public static JPanel panel1, panel2, panel3, panel4;
   public static JLabel main1, main2, label1, label2,label3,label4,image;
   public static JTextField number1, number2;
   public static JTextArea output;
   public static JButton calculate,exit;
   public static String input="Enter"; 
   public static int position;
String num="";
public RomanNumeralCalculator()
{
    super ("Roman Numeral Calculator");
    setSize(1045,740);
    setLocation(0,0);
    Container container = getContentPane();
    container.setBackground(Color.GREEN);

    JLabel image=new JLabel(new ImageIcon("romanNumerals.jpg"));

    panel1=new JPanel();
    panel2=new JPanel();
    panel3=new JPanel();
    panel4=new JPanel();

    panel1.setLayout(new GridLayout(2,7));
    panel1.setBackground(Color.GREEN);
    panel2.setLayout(new FlowLayout());
    panel2.setBackground(Color.MAGENTA);
    panel3.setLayout(new FlowLayout());
    panel3.setBackground(Color.YELLOW);
    panel4.setLayout(new FlowLayout());
    panel4.setBackground(Color.GRAY);

    JLabel main1=new JLabel("Welcome To The Roman Numerals Calculator");
    JLabel main2=new JLabel("BY: Harpreet Singh, Date: 31/10/2013");

    label3=new JLabel("Here are the following numbers that can be used in the calculator:");
    label4=new JLabel("I=1 , V=5 , X=10 , L=50 , C=100 , D=500 , M=1000");

    calculate=new JButton("Calculate");
    exit=new JButton("Exit");

    ButtonHandler handler = new ButtonHandler();
    calculate.addActionListener(handler);
    exit.addActionListener(handler);

    label1=new JLabel("Enter first number in roman numerals:");
    number1=new JTextField("",10);
    label2=new JLabel("Enter second number in roman numerals:");
    number2=new JTextField("",10);

    output=new JTextArea(10,100);
    output.setEditable(false);

    container.setLayout(new BorderLayout());
    container.add(panel1, BorderLayout.NORTH);
    container.add(panel2, BorderLayout.CENTER);
    container.add(panel3, BorderLayout.SOUTH);

    panel1.add(main1);
    panel1.add(main2);
    panel1.add(image);
    panel2.add(label3);
    panel2.add(label4);
    panel3.add(label1);
    panel3.add(number1);
    panel3.add(label2);
    panel3.add(number2);
    panel3.add(calculate);        
    panel3.add(exit);

    setVisible(true);
}

public class ButtonHandler implements ActionListener
{
    public void actionPerformed(ActionEvent e)
    {
        if (e.getSource()==calculate)
        {
            String num1=number1.getText();
            String num2=number2.getText();
            CalculateNumbers x=new CalculateNumbers();
            x.calculations(num1,num2);
        }
        else if (e.getSource()==exit)
        {
            System.exit(0);
        }
    }
}

public static void main (String args[])
{
    /*String choice=JOptionPane.showInputDialog(null, "Please Type In 'Enter' to Continue: ", "Enter", JOptionPane.PLAIN_MESSAGE);
    if ((choice == null) || ((choice != null) && !(choice.equalsIgnoreCase(input))))
    {
    JOptionPane.showMessageDialog(null, "Invalid Password. Please Try Again.");
    System.exit(0);
    }*/
    //else
    //{
    //JOptionPane.showMessageDialog(null, "Correct Password");
    RomanNumeralCalculator application = new RomanNumeralCalculator();
    //}
}

}

You'll want two functions: One that takes a String (the roman numeral) and returns a number, and the other that takes a number and returns a String (the roman numeral). So you'd take your two inputs, pass them to your first function to convert to numbers, add them together, then pass the result to your second function to get the result as a roman numeral. — Anthony Grist, Nov 05 '13 at 15:12
Use a switch, map, or implement a parser to convert the numbers. — Zong, Nov 05 '13 at 15:12
how would i do that because my main way of entering numbers is a text field — help for ICS, Nov 05 '13 at 15:14

score 4 · Answer 1 · edited May 23 '17 at 10:26

4

first write two methods

convert Roman number to regular number
convert regular number to roman number

when ever user provide input in roman number convert them to regular number perform arithmetic operation and finally convert the result to roman number

Also check Converting Roman Numerals To Decimal and Convert Int to Roman Numeral

edited May 23 '17 at 10:26

Community

1
1

answered Nov 05 '13 at 15:14

upog

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cant i use two methods instead – help for ICS Nov 05 '13 at 15:16
can u help me get started on one method because i am new to java and also kind of condused as to how i would do this – help for ICS Nov 05 '13 at 15:21
I understood it will be big task to finish. The links i shared has answers and explanation, please go through them – upog Nov 05 '13 at 15:25
can u help me convert the total which is an integer to its equivalent roman numeral – help for ICS Nov 12 '13 at 16:05

score 0 · Answer 2 · answered Nov 05 '13 at 15:16

Create a roman number class that will convert your number given a decimal number and vise versa. You can even make it static if you want.

This will make your code look nicer and more object oriented.

There is an algorithm explained here.

roman number algorithm

score 0 · Answer 3 · answered Nov 05 '13 at 15:30

       import java.util.Scanner;

        public class Roman {

        public static void main(String[] args) {

        Scanner stdIn = new Scanner(System.in);

         System.out.print("Enter a Roman Number:> ");

          char[] roman = stdIn.nextLine().toCharArray();

    int total = 0;
    for(int i = roman.length-1; i > -1; i--){
        switch(roman[i]){
            case 'I':
                total += value(roman[i]); break;
            case 'V':
            case 'X':
            case 'L':
            case 'C':
            case 'D':
            case 'M':
                if(i != 0 && (value(roman[i-1]) < value(roman[i]))){
                    total += value(roman[i]) - value(roman[i-1]);
                    i--;
                }else{
                    total += value(roman[i]);
                }
                break;
        }
    }
    System.out.println(total);
}

public static int value(char c){
    switch(c){
        case 'I':
            return 1;
        case 'V':
            return 5;
        case 'X':
            return 10;
        case 'L':
            return 50;
        case 'C':
            return 100;
        case 'D':
            return 500;
        case 'M':
            return 1000;
        default:
            return 0;
    }
} }

after compiling when "Enter a Roman No. " message comes , Enter for example : M+V and it will add it — scavy, Nov 05 '13 at 15:33

how to add roman numbers in java

3 Answers3