Question

我正在制作阿拉伯语到罗马数字转换器并收到错误：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
    at arab2Roman.arabicToRoman(arab2Roman.java:27)
    at arab2Roman.main(arab2Roman.java:178)

非常感谢任何建议/反馈。

public class arab2Roman {

    public static String arabicToRoman(int Arabic) {
        if (Arabic==-1) {
            System.out.println("Program exiting...");
            System.exit(0);
        } else if (Arabic<=0) {
            return "Invalid Option: Must be greater than 0";
        } else if (Arabic>=4000) {
            return "Invalid Option: Must be under 4000.";
        } else {
            String banana = new String();
            String temp = Integer.toString(Arabic);
            int[] arabArray = new int[temp.length()];
            for (int i = 0; i < temp.length(); i++) {
                arabArray[i] = temp.charAt(i) - '0';
            } 
            int o = 0;
            char[] romanArray = new char[o];
            for (int i=0;i<temp.length();) {
                if (temp.length()==4) {
                    if (arabArray[0]==3) {
                        for (;o<3;o++) {
                            romanArray[o] = 'M';    
                        }
                    } else if (arabArray[0]==2) {
                        for (;o<2;o++) {
                            romanArray[o] = 'M';    
                        }
                    } else if (arabArray[0]==1) {
                        romanArray[0]= 'M';
                    }
                    if (arabArray[1]==9) {
                        romanArray[o]='C';
                        o++;
                        romanArray[o]='M';
                        o++;
                    } else if (arabArray[1]==8) {
                        romanArray[o]='D';
                        o++;
                        for (int p=o;o<p+3;o++) {
                            romanArray[o]='C';
                        }
                    } else if (arabArray[1]==7) {
                        romanArray[o]='D';
                        o++;
                        for (int p=o;o<p+2;o++) {
                            romanArray[o]='C';
                        }
                    } else if (arabArray[1]==6) {
                        romanArray[o]='D';
                        o++;
                        romanArray[o]='C';
                        o++;
                    } else if (arabArray[1]==5) {
                        romanArray[o]='D';
                        o++;
                    } else if (arabArray[1]==4) {
                        romanArray[o]='C';
                        o++;
                        romanArray[o]='D';
                        o++;
                    } else if (arabArray[1]==3) {
                        for (int p=o;o<p+3;o++) {
                            romanArray[o]='C';
                        }
                    } else if (arabArray[1]==2) {
                        for (int p=o;o<p+2;o++) {
                            romanArray[o]='C';
                        }
                    } else if (arabArray[1]==1) {
                        romanArray[o]='C';
                        o++;
                    }
                    if (arabArray[2]==9) {
                        romanArray[o]='X';
                        o++;
                        romanArray[o]='C';
                        o++;
                    } else if (arabArray[2]==8) {
                        romanArray[o]='L';
                        o++;
                        for (int p=o;o<p+3;o++) {
                            romanArray[o]='X';
                        }
                    } else if (arabArray[2]==7) {
                        romanArray[o]='L';
                        o++;
                        for (int p=o;o<p+2;o++) {
                            romanArray[o]='X';
                        }
                    } else if (arabArray[2]==6) {
                        romanArray[o]='L';
                        o++;
                        romanArray[o]='X';
                        o++;
                    } else if (arabArray[2]==5) {
                        romanArray[o]='L';
                        o++;
                    } else if (arabArray[2]==4) {
                        romanArray[o]='X';
                        o++;
                        romanArray[o]='L';
                        o++;
                    } else if (arabArray[2]==3) {
                        for (int p=o;o<p+3;o++) {
                            romanArray[o]='X';
                        }
                    } else if (arabArray[2]==2) {
                        for (int p=o;o<p+2;o++) {
                            romanArray[o]='X';
                        }
                    } else if (arabArray[2]==1) {
                        romanArray[o]='X';
                        o++;
                    }
                    if (arabArray[3]==9) {
                        romanArray[o]='I';
                        o++;
                        romanArray[o]='X';
                        o++;
                    } else if (arabArray[3]==8) {
                        romanArray[o]='V';
                        o++;
                        for (int p=o;o<p+3;o++) {
                            romanArray[o]='I';
                        }
                    } else if (arabArray[3]==7) {
                        romanArray[o]='V';
                        o++;
                        for (int p=o;o<p+2;o++) {
                            romanArray[o]='I';
                        }
                    } else if (arabArray[3]==6) {
                        romanArray[o]='V';
                        o++;
                        romanArray[o]='I';
                        o++;
                    } else if (arabArray[3]==5) {
                        romanArray[o]='V';
                        o++;
                    } else if (arabArray[3]==4) {
                        romanArray[o]='I';
                        o++;
                        romanArray[o]='V';
                        o++;
                    } else if (arabArray[3]==3) {
                        for (int p=o;o<p+3;o++) {
                            romanArray[o]='I';
                        }
                    } else if (arabArray[3]==2) {
                        for (int p=o;o<p+2;o++) {
                            romanArray[o]='I';
                        }
                    } else if (arabArray[3]==1) {
                        romanArray[o]='I';
                        o++;
                    }
                    banana = new String(romanArray);
                    i++;
                    return banana;
                }
            }
        }
        return null;
    }

    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner dog = new Scanner(System.in);
        for (int i=0;i==0;) {
            System.out.println("Enter a number (1-3996) to convert to Roman Numberals(enter -1 to exit):");
            int Arabic = dog.nextInt();
            System.out.println(arabicToRoman(Arabic));
        }
    }
}

Answer 1

这里有很多东西可以改进/简化，但看起来主要问题是：

int o = 0;
char[] romanArray = new char[o];

这是创建一个大小为0的数组，因此romanArray[0]进一步向下越界。

Answer 2

这是我最终得到的算法。

import java.util.HashMap;

public class SimpleRomanConverter {
    private static final HashMap<Integer, String> romanSymbolsMap = createRomanMap();
    private static HashMap<Integer, String> createRomanMap() {
        HashMap<Integer, String> map = new HashMap<Integer, String>();
        map.put(1, "I");
        map.put(4, "IV");
        map.put(5, "V");
        map.put(9, "IX");
        map.put(10, "X");
        map.put(40, "XL");
        map.put(50, "L");
        map.put(90, "XC");
        map.put(100, "C");
        map.put(400, "CD");
        map.put(500, "D");
        map.put(900, "CM");
        map.put(1000, "M");
        return map;
    }

    public String convert(int number) throws RomanNumberOutOfRangeException {
        if (number < 0 || number > RomanNumbersInfo.MAX_ROMAN_ALLOWED)
            throw new RomanNumberOutOfRangeException();

        if(number == 0)
            return "";

        return find(number);
    }

    private String find(int number) {
        if(romanSymbolsMap.containsKey(number))
            return romanSymbolsMap.get(number);

        int nearest = number;
        while (!romanSymbolsMap.containsKey(nearest) && nearest != 0)
            nearest--;

        return romanSymbolsMap.get(nearest) + find(number - nearest);
    }
}

阿拉伯语到罗马语转换器：ArrayIndexOutOfBounds

2 个答案: