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Java Forum / First Aid / December 2006a way of converting a roman numeral into an integer
Hi i'm fairly new to java and have been assigned to create a basic application which converts a roman numeral inputted by a user and then outputs the corresponding number (integer). Any tips on how to do this will be much appriciated. I was thinking of doing an array for each numeral and number but again i can't really work this out till i figure out how to convert the numeral into an integer. Thanks > Hi i'm fairly new to java and have been assigned to create a basic > application which converts a roman numeral inputted by a user and then [quoted text clipped - 4 lines] > i can't really work this out till i figure out how to convert the > numeral into an integer. Presumably, you mean you want to convert an ASCII representation of the roman numerals, so that the 4-character string "VIII" represents 8, as opposed to using the Unicode single character representation for roman numeral eight. Do you know how to use a switch statement? - Oliver Oliver, thanks for the reply. I have a rough idea on switch statements, i have some books with explanations so i can look over them, would you recommend having different cases for each Numeral? Or which way of doing it would you recommend? I was going to have something like this before within the code, char c represents the character the user has input. static int convertRoman(char c) { if (c=='I') return 1; if (c=='V') return 5; if (c=='X') return 10; if (c=='L') return 50; if (c=='C') return 100; if (c=='D') return 500; if (c=='M') return 1000; return 0; } > > Hi i'm fairly new to java and have been assigned to create a basic > > application which converts a roman numeral inputted by a user and then [quoted text clipped - 13 lines] > > - Oliver [post re-ordered for clarity] >> > Hi i'm fairly new to java and have been assigned to create a basic >> > application which converts a roman numeral inputted by a user and then [quoted text clipped - 12 lines] >> >> Do you know how to use a switch statement? [...] > static int convertRoman(char c) > { [quoted text clipped - 7 lines] > return 0; > } Right, this is pretty much what I intended (although you used an if statement instead of a switch statement). If you're familiar with exceptions, it might be a good idea to throw an exception instead of returning 0 if the input doesn't match any of the predefined letters. If you're not familiar with exceptions, then don't worry about that for now, as your code is fine as it is. The next step is tricky, mainly because the roman numeral system has some pretty strange rules. Is this for an official school assignment, or are you just exploring on your own? If the latter, I recommend you pause this task and try something easier, like converting an integer to its textual representation. E.g. given the integer 1234, produce the string "one thousand two hundred thirty four". Once you can do that, come back to this roman numeral exercise. - Oliver It is an assignment so yeah I need to get it done really, thanks for the help though i'll just stick at it hopefully it'll come to me soon enough. > It is an assignment so yeah I need to get it done really, thanks for > the help though i'll just stick at it hopefully it'll come to me soon > enough. If it were up to me, I'd try to formalize and articulate the rules for converting roman numerals to numbers in plain English, and once I have it all written down in English (or whatever natural language you're most comfortable with), it'll be easier to try to translate that into Java. For example, I might notice that If you have a series of Is, you can sum them up, so that "I" is 1, "II" is 1+1=2, and so on. But if the Is appear before a "bigger" character, their sum will get subtracted from that bigger character, so IV is 5-1=4, or IX is 10-1=9. This is an important step because if you don't even know what all the rules are, there's no way you can possibly write a program that'll implement all the rules. - Oliver Oliver, thanks for the reply. I have a rough idea on switch statements, i have some books with explanations so i can look over them, would you recommend having different cases for each Numeral? Or which way of doing it would you recommend? I was going to have something like this before within the code, char c represents the character the user has input. static int convertRoman(char c) { if (c=='I') return 1; if (c=='V') return 5; if (c=='X') return 10; if (c=='L') return 50; if (c=='C') return 100; if (c=='D') return 500; if (c=='M') return 1000; return 0; } > > Hi i'm fairly new to java and have been assigned to create a basic > > application which converts a roman numeral inputted by a user and then [quoted text clipped - 13 lines] > > - Oliver > Hi i'm fairly new to java and have been assigned to create a basic > application which converts a roman numeral inputted by a user and then [quoted text clipped - 6 lines] > > Thanks AP Computer Science is supposed to be for people who have at least some idea what they're doing. I'll admit some of the stuff that's covered for the test is complicated, and people might need help (sorting and searching come to mind). But for something as simple as converting a roman numeral to an integer, you should be ashamed of yourself. Think about it this way: how do /you/ convert a roman numeral into an arabic number? Write down the rules that you use in your head, then convert that to code. Use some for loops, no arrays are needed. Do your own homework from now on! Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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