Question

Lab 4: Java Fundamentals, Part IV

In this assignment, you solve a conversion problem similar to Programming Challenge 1 of Chapter 3 of your text, page 184 (187 in Edition 5). Given one of the Roman numerals I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV as an input your program must determine and display the corresponding decimal digit 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15.

Book = Tony Gaddis: Starting Out with Java, From Control Structures Through Objects, 7th Edition

^Requirements

0. The solution must use a nested if – else construct built as follows:

1. The top level if-else decision is made upon the first character of the Roman numeral, which is always ‘I’ or ‘V’ or ‘X’. That is, divide the given group of Roman numerals into three subgroups according to their first character either ‘I’ or ‘V’ or ‘X’.

2. Both the if and else blocks contain deeply nested if-else structures where the input string is compared to the Roman numerals I, II, III, IV, IX in the first block and to V, VI, VII, VIII in the second block, and then to X, XI, XII, XIII, XIV, XV in the third block.

• Input is solicited on a dialog window as shown on Figure 1.

• _{Figure 1 = "Input a Roman Numeral between "I" and "XV"}

• Declare a String variable title to store the title text such as “Conversion of Roman numerals”. Declare a String variable task to store the input solicitation text, such as “Enter a Roman numeral between “I” and “XV” ”. In the showInputDialog() method call that creates the window you must use the variables. For example, JOptionPane.showInputDialog(null, task, title, JOptionPane.QUESTION_MESSAGE). The input window must follow the template of Figure 1.

• Declare a String variable roman to save the input string returned by the window.

• Declare an int variable decimal to store the decimal digit equivalent of the roman numeral and

  initialize to 0.

• Allow to use lowercase or uppercase, even mixed characters as input Roman numerals. The output Roman numerals must be in upper case. Use toUpperCase() for the conversions (see page 74).

• The output must be displayed on a message dialog as shown on Figure 2 and the output window must follow the template, take note of the title line and the output arrangement. Use String.format() method for the output arrangement, such as “The decimal value for the Roman numeral “VIII” is: ....... 8 ......” in two lines. (See the String.format in page 175-176).

• _{Figure 2 = "The decimal value for the roman numeral "XIII" is: .....8....."}

We assume that the input string is not empty and not null (each triggers a runtime error)

• If the input string is none of the fifteen admissible Roman numerals, the message as shown on Figure 3 is displayed

• _{Figure 3 = "input XIX is not an admissible Roman Numeral"}

• When you check the first character, use the == operator for equality an do not forget the character operator on the literal, put roman.charAt(0) == ‘I’ into the topmost if header. (hints)

• Use the equals method for string comparison (see pp 146-147 in your book). A nested if header shall look like (hints)

       if(roman.equals(“VII”)){
  

• The output text (see Figure 2) contains the “ ” symbols. Use the escape sequence \” within the

  text. (hints)

• Use do-while loop and the showConfirmDialog() method, such as “int yesNo =JOptionPane.showConfirmDialog(null, "Any more Roman Numerals? \nyes or no", title,JOptionPane.YES_NO_OPTION);” asking whether the process be continued as shown in Figure 4.

•

_{Figure 4 = "Any more Roman Numerals? Yes or No"}

Finally, before the program ends, a message is displayed through the message box as shown in Figure 5.

_{Figure 5 = "End of Program!"}

For JOptionPane class, you need to use the following two statements in a proper location. Do not excessively state System.exit(0); before the end of the main method. The import statement must be placed well top before the “public class RomanNumerals{...}”.

import javax.swing.JOptionPane; //needed for JOptionPane class.

and
System.exit(0); //required JOptionPane class

Answer 1

// Program to convert Roman Numerals to Numbers
import java.util.*;
  
public class RomanToNumber
{
// This function returns value of a Roman symbol
int value(char r)
{
if (r == 'I')
return 1;
if (r == 'V')
return 5;
if (r == 'X')
return 10;
if (r == 'L')
return 50;
if (r == 'C')
return 100;
if (r == 'D')
return 500;
if (r == 'M')
return 1000;
return -1;
}
  
// Finds decimal value of a given romal numeral
int romanToDecimal(String str)
{
// Initialize result
int res = 0;
  
for (int i=0; i<str.length(); i++)
{
// Getting value of symbol s[i]
int s1 = value(str.charAt(i));
  
// Getting value of symbol s[i+1]
if (i+1 <str.length())
{
int s2 = value(str.charAt(i+1));
  
// Comparing both values
if (s1 >= s2)
{
// Value of current symbol is greater
// or equalto the next symbol
res = res + s1;
}
else
{
res = res + s2 - s1;
i++; // Value of current symbol is
// less than the next symbol
}
}
else
{
res = res + s1;
i++;
}
}
  
return res;
}
  
// Driver method
public static void main(String args[])
{
RomanToNumber ob = new RomanToNumber();
  
// Considering inputs given are valid
String str = "MCMIV";
System.out.println("Integer form of Roman Numeral" + " is " + ob.romanToDecimal(str));
}
}