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  1. class Test {
  2.  
  3.     private static String toDecimal(String hex, int numberDigits) {
  4.         /* converts a string such as "13.1a" in base 16 to "19.1015625" in base 10 */
  5.         int index = hex.indexOf('.');
  6.         assert index != -1;
  7.         StringBuilder decimal = new StringBuilder((index == 0) ? "" : String.valueOf(Integer.parseInt(hex.substring(0, index), 16)));
  8.         decimal.append('.');
  9.         int l = hex.length() - index - 1;
  10.         assert l >= 1;
  11.         int firstIndex = index + 1;
  12.         int hexDigits[] = new int[l];
  13.         for (int i = 0; i < l; i++) {
  14.             hexDigits[i] = Integer.parseInt(hex.substring(i + firstIndex, i + firstIndex + 1), 16);
  15.         }
  16.         while (numberDigits != 0 && l != 0) {
  17.             int carry = 0;
  18.             boolean allZeroes = true;
  19.             for (int i = l - 1; i >= 0; i--) {
  20.                 int value = hexDigits[i] * 10 + carry;
  21.                 if (value == 0 && allZeroes) {
  22.                     l = i;
  23.                 }
  24.                 else {
  25.                     allZeroes = false;
  26.                     carry = (int)(value / 16);
  27.                     hexDigits[i] = value % 16;
  28.                 }
  29.             }
  30.             numberDigits--;
  31.             if (carry != 0 || (numberDigits != 0 && l != 0))
  32.                 decimal.append("0123456789".charAt(carry));
  33.         }
  34.         return decimal.toString();
  35.     }
  36.  
  37.     public static void main(String[] args) {
  38.         System.out.println(toDecimal("13.1a", 15));
  39.         System.out.println(toDecimal("13.8", 15));
  40.         System.out.println(toDecimal("13.1234", 15));
  41.     }
  42.  
  43. }
Success #stdin #stdout 0.06s 32440KB
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Standard input is empty
stdout
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19.1015625
19.5
19.07110595703125
https://ideone.com/LpPu0c
language:
Java (12.0.1)
created:
3 years ago
visibility:
public

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