java - java将罗马数字转换为数字逻辑错误

Question

所以我有一个家庭作业，我必须能够获取罗马数字并进行相反的转换。我知道如何从数字到字母，但字母到数字让我很困惑。我需要帮助，因为我编写了我的程序和罗马数字来进行数字工作。例如，如果我尝试执行 XCIX == 99，我会得到 199。但如果我用罗马数字表示2014，那就有效了。另外，如果我只输入一个字母，我会得到0。我只需要帮助了解我需要做什么来解决问题。

import java.util.HashMap;
import java.util.Scanner;

public class Apweek2 {

public static void main(String[] args) {
    Scanner userinput = new Scanner(System.in);
    System.out.print("enter a number to convert to roman numerals: ");
    int input = userinput.nextInt();

    String[] rv = { "I", "IV", "V", "IX", "X", "XL", "L", "XC", "C", "CD",
            "D", "CM", "M" };
    int[] values_for_rv = { 1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900,
            1000 };

    System.out.print("enter a roman numeral: ");
    String roman_numeral = userinput.next();

    int sum = 0;
    String two_spot = null;
    String last_value = null;
    for (int i = 1, j = 0; j < roman_numeral.length()
            && i < roman_numeral.length(); i++, j++) {

        last_value = roman_numeral.substring(j, i);

        char roman_noodles = roman_numeral.charAt(i);
        char raman_noodles = roman_numeral.charAt(j);

        String roman_values = Character.toString(roman_noodles);

        two_spot = last_value + roman_values;

        if (two_spot.contains(rv[1])) {
            sum = sum + values_for_rv[1];
        }
        if (two_spot.contains(rv[3])) {
            sum = sum + values_for_rv[3];
        }
        if (two_spot.contains(rv[5])) {
            sum = sum + values_for_rv[5];
        }
        if (two_spot.contains(rv[7])) {
            sum = sum + values_for_rv[7];
        }
        if (two_spot.contains(rv[9])) {
            sum = sum + values_for_rv[9];
        }
        if (two_spot.contains(rv[11])) {
            sum = sum + values_for_rv[11];
        }

        if (!(two_spot.equals(rv[1])) && !(two_spot.equals(rv[3]))
                && !(two_spot.equals(rv[5])) && !(two_spot.equals(rv[7]))
                && !(two_spot.equals(rv[9])) && !(two_spot.equals(rv[11]))) {

            if (raman_noodles == 'I') {
                sum = sum + 1;
            }
            if (raman_noodles == 'V') {
                sum = sum + 5;
            }
            if (raman_noodles == 'X') {
                sum = sum + 10;
            }
            if (raman_noodles == 'L') {
                sum = sum + 50;
            }
            if (raman_noodles == 'C') {
                sum = sum + 100;
            }
            if (raman_noodles == 'D') {
                sum = sum + 500;
            }
            if (raman_noodles == 'M') {
                sum = sum + 1000;
            }

        }

    }
    System.out.println("converted roman numeral is: " + sum);

    String inputconversion = inputtoroman(input);

    System.out.print("Converted number is: " + inputconversion);
}

public static String inputtoroman(int x) {

    String s1 = "";
    String s2 = "";
    String s3 = "";
    String s4 = "";
    String s5 = "";
    String s6 = "";
    String s7 = "";
    String s8 = "";
    String s9 = "";
    String s10 = "";
    String s11 = "";
    String s12 = "";
    String s13 = "";

    while (x >= 1000) {
        s1 += "M";
        x -= 1000;
    }
    while (x >= 900) {
        s2 += "CM";
        x -= 900;
    }
    while (x >= 500) {
        s3 += "D";
        x -= 500;
    }
    while (x >= 400) {
        s4 += "CD";
        x -= 400;
    }
    while (x >= 100) {
        s5 += "C";
        x -= 100;
    }
    while (x >= 90) {
        s6 += "XC";
        x -= 90;
    }
    while (x >= 50) {
        s7 += "L";
        x -= 50;
    }
    while (x >= 40) {
        s8 += "XL";
        x -= 40;
    }
    while (x >= 10) {
        s9 += "X";
        x -= 10;
    }
    while (x >= 9) {
        s10 += "IX";
        x -= 9;
    }
    while (x >= 5) {
        s11 += "V";
        x -= 5;
    }
    while (x >= 4) {
        s12 += "IV";
        x -= 4;
    }
    while (x >= 1) {
        s13 += "I";
        x -= 1;
    }
    String combined = s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10
            + s11 + s12 + s13;
    return combined;

}
}

Answer 1

你从1开始，所以当你只输入1个数字时，它根本不会进入循环。应更改为与 roman_numeral 的全长进行比较。

for (int i = 1, j = 0; j < roman_numeral.length()
        && i <= roman_numeral.length(); i++, j++) {

这可能也会影响它的循环方式，但我目前无法自己运行它。

编辑:实际上，再看一遍，我已经可以看到它会在 char roman_noodles = roman_numeral.charAt(i); 上崩溃。

如果您希望它仅检查 1 个字符，则需要添加一些额外的逻辑。