การแปลงตัวเลขสากลเป็นตัวเลขโรมันใน Java

หากพูดถึงตัวเลขโรมัน หลายๆคนอาจจะรู้อยู่แล้ว หรือหลายๆคนอาจจะจำไม่ได้ แต่หากพูดถึงตัวเลข "I" บนหน้าปัดนาฬิกา บางคนอาจจะนึกออก จริงๆแล้วตัวเลขโรมันมีตั้งแต่เลข 1 - 3999 เท่านั้นครับ เพื่อไม่ให้เสียเวลา เรามาดูตัวอย่างกันครับ

ตัวอย่างโคด 

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package demo;      import java.math.BigDecimal;     /**  * @author nopphanan7  *  ตัวเลขโรมันมีค่าตั้งแต่ 1 ถึง 3999 เท่านั้น  */  public final class RomanNumber {              private static final String[] ROMAN = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX","V", "IV", "I"};     private static final int[] DIGIT = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};         private String valueText;          // ···········Methods··············      public String getText(int amount) {          BigDecimal value = new BigDecimal(amount);          this.valueText = getRomanNumber(value);          return this.valueText;      }          public String getText(long amount) {          BigDecimal value = new BigDecimal(amount);          this.valueText = getRomanNumber(value);          return this.valueText;      }          public String getText(String amount) {         BigDecimal value = new BigDecimal(amount.trim());          this.valueText = getRomanNumber(value);          return this.valueText;      }          public String getText(Number amount) {          BigDecimal value = new BigDecimal(String.valueOf(amount));          this.valueText = getRomanNumber(value);          return this.valueText;      }          private static String getRomanNumber(BigDecimal amount) {         String roman = "";         if (amount.compareTo(BigDecimal.ONE) < 0) {             return "Value of RomanNumeral must be positive.";         }         if (amount.compareTo(BigDecimal.valueOf(new Long("3999"))) > 0 ) {             return "Value of RomanNumeral must be 3999 or less.";         }         int N = Integer.parseInt(amount.toString());         for (int i = 0; i < DIGIT.length; i++) {            while (N >= DIGIT[i]) {               roman += ROMAN[i];               N -= DIGIT[i];            }         }         return roman;     }              /**      * @param args      */      public static void main(String[] args) {       System.out.println("value of 1 : " + new RomanNumber().getText(1));      System.out.println("value of 2 : " + new RomanNumber().getText(2));         System.out.println("value of 3 : " + new RomanNumber().getText(3));          System.out.println("value of 4 : " + new RomanNumber().getText(4));         System.out.println("value of 5 : " + new RomanNumber().getText(5));         System.out.println("value of 6 : " + new RomanNumber().getText(6));         System.out.println("value of 7 : " + new RomanNumber().getText(7));          System.out.println("value of 8 : " + new RomanNumber().getText(8));         System.out.println("value of 9 : " + new RomanNumber().getText(9));         System.out.println("value of 10 : " + new RomanNumber().getText(10));         System.out.println("value of 123 : " + new RomanNumber().getText("123"));          System.out.println("value of 3234 : " + new RomanNumber().getText("3234"));      }      }

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value of 1 : I value of 2 : II value of 3 : III value of 4 : IV value of 5 : V value of 6 : VI value of 7 : VII value of 8 : VIII value of 9 : IX value of 10 : X value of 123 : CXXIII value of 3234 : MMMCCXXXIV

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