Roman Numeral Converter Problem

[uberwalla]

Hey there thanks to those that have helped me through some of this with commands I didn't know. Trying to move into java from extensive javaSCRIPT is hard. A lot of different forms.

Anyways this is what i have so far:

Java:

import java.util.Scanner; public class Assignment05 {              public static void main (String [] args) {                 String [] ones = new String [10];                         ones [0] = "";                         ones [1] = "I";                         ones [2] = "II";                         ones [3] = "III";                         ones [4] = "IV";                         ones [5] = "V";                         ones [6] = "VI";                         ones [7] = "VII";                         ones [8] = "VIII";                         ones [9] = "IX";                                         String [] tens = new String [10];                         tens [0] = "";                         tens [1] = "X";                         tens [2] = "XX";                         tens [3] = "XXX";                         tens [4] = "XL";                         tens [5] = "L";                         tens [6] = "LX";                         tens [7] = "LXX";                         tens [8] = "LXXX";                         tens [9] = "XC";                                         String [] hundreds = new String [10];                         hundreds [0] = "";                         hundreds [1] = "C";                         hundreds [2] = "CC";                         hundreds [3] = "CCC";                         hundreds [4] = "CD";                         hundreds [5] = "D";                         hundreds [6] = "DC";                         hundreds [7] = "DCC";                         hundreds [8] = "DCCC";                         hundreds [9] = "CM";                                         String [] thousands = new String [4];                         thousands [0] = "";                         thousands [1] = "M";                         thousands [2] = "MM";                         thousands [3] = "MMM";                                         String [][] all = new String [4][];                         all [0] = ones;                         all [1] = tens;                         all [2] = hundreds;                         all [3] = thousands;                                         String roman = "";                                         Scanner input = new Scanner(System.in);                         System.out.print("Enter a year, and I will convert it to roman numerals: ");         int year = input.nextInt();                 String yearStr = Integer.toString(year);         int length = yearStr.length();                 for (int i = 0; i < length; i++) {                 roman += all[length - i - 1][yearStr.charAt(i)];         }         System.out.format(roman);         } }

The code compiles fine but when I run it and enter a number i get the error:

Java:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 51             at Assignment05.main(Assignment05.java:70)

any idea what i can do to fix this?

[OneOffDriveByPoster]

code:

roman += all[length - i - 1][yearStr.charAt(i)];

yearStr.charAt(i) returns a char. '3' == 51. You need use Integer.toString() or something like yearStr.charAt(i) - '0'.

[uberwalla]

ok must ask how do i use the Integer.toString to my charAt? i tried using it like:

yearStr.charAt(Integer.toString(i))

but i got an error.

i am quite lost

[OneOffDriveByPoster]

Try Integer.toString(yearStr.substring(i, i + 1)).

[uberwalla]

i have no idea what this means: (its what i get using substring)

Java:

Assignment05.java:70: cannot find symbol symbol  : method toString(java.lang.String) location: class java.lang.Integer                 roman += all[length - i - 1][Integer.toString(yearStr.substring(i, i + 1))];                                                      ^ 1 error

[OneOffDriveByPoster]

ugh, my fault: Integer.parseInt instead.

[uberwalla]

thanks a lot man. i actually found another way around this.

Java:

import java.util.Scanner; public class Assignment05 {              public static void main (String [] args) {                 String [] ones = new String [10];                         ones [0] = "";                         ones [1] = "I";                         ones [2] = "II";                         ones [3] = "III";                         ones [4] = "IV";                         ones [5] = "V";                         ones [6] = "VI";                         ones [7] = "VII";                         ones [8] = "VIII";                         ones [9] = "IX";                                         String [] tens = new String [10];                         tens [0] = "";                         tens [1] = "X";                         tens [2] = "XX";                         tens [3] = "XXX";                         tens [4] = "XL";                         tens [5] = "L";                         tens [6] = "LX";                         tens [7] = "LXX";                         tens [8] = "LXXX";                         tens [9] = "XC";                                         String [] hundreds = new String [10];                         hundreds [0] = "";                         hundreds [1] = "C";                         hundreds [2] = "CC";                         hundreds [3] = "CCC";                         hundreds [4] = "CD";                         hundreds [5] = "D";                         hundreds [6] = "DC";                         hundreds [7] = "DCC";                         hundreds [8] = "DCCC";                         hundreds [9] = "CM";                                         String [] thousands = new String [4];                         thousands [0] = "";                         thousands [1] = "M";                         thousands [2] = "MM";                         thousands [3] = "MMM";                                         String [][] all = new String [4][];                         all [0] = ones;                         all [1] = tens;                         all [2] = hundreds;                         all [3] = thousands;                                         String roman = "";                                         Scanner input = new Scanner(System.in);                         System.out.print("Enter a year, and I will convert it to roman numerals: ");         int year = input.nextInt();                 String yearStr = Integer.toString(year);         int length = yearStr.length();                 for (int i = 0; i < length; i++) {                 roman += all[length - i - 1][Integer.valueOf(yearStr.substring(i,i+1))];         }         System.out.print(roman + "\n");         } }

thanks for all your help

[richcash]

If you have time/interest, try to shorten your program and significantly reduce the memory your program uses. You do not need to store all of those values in those arrays. Use some recursion (and math). And you also don't need to do the costly conversion of integer to string.

[uberwalla]

well i am still relatively new to java so i do not know how to easily reduce the program. i mostly know some of the commands from c/c++ and javascript, because they are relatively close. but java is still weird to me in how you have to format the code and such.