阿拉伯語羅馬轉換器：

Question

的ArrayIndexOutOfBounds

我想提出一個阿拉伯語的羅馬數字轉換器和得到的錯誤：

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

任何建議/反饋我們將不勝感激。

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

有很多的東西可以改進/這裏簡化，但它看起來像的主要問題是：

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

這是創建大小爲0的數組，從而romanArray[0]是進一步下降。

Answer 2

這是我結束的算法。

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); 
    } 
}