choiceformat.java

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   *
   * @return The <code>StringBuffer</code> with the format string appended.
   */
  public StringBuffer format (double num, StringBuffer appendBuf,
			      FieldPosition pos)
  {
    if (choiceLimits.length == 0)
      return appendBuf;

    int index = 0;
    if (! Double.isNaN(num) && num >= choiceLimits[0])
      {
	for (; index < choiceLimits.length - 1; ++index)
	  {
	    if (choiceLimits[index] <= num && num < choiceLimits[index + 1])
	      break;
	  }
      }

    return appendBuf.append(choiceFormats[index]);
  }

  /**
   * This method returns the list of format strings in use.
   *
   * @return The list of format objects.
   */
  public Object[] getFormats ()
  {
    return (Object[]) choiceFormats.clone();
  }

  /**
   * This method returns the list of range terminators in use.
   *
   * @return The list of range terminators.
   */
  public double[] getLimits ()
  {
    return (double[]) choiceLimits.clone();
  }

  /**
   * This method returns a hash value for this object
   * 
   * @return A hash value for this object.
   */
  public int hashCode ()
  {
    int hash = 0;
    for (int i = 0; i < choiceLimits.length; ++i)
      {
	long v = Double.doubleToLongBits(choiceLimits[i]);
	hash ^= (v ^ (v >>> 32));
	hash ^= choiceFormats[i].hashCode();
      }
    return hash;
  }

  /**
   * This method returns the lowest possible double greater than the 
   * specified double.  If the specified double value is equal to
   * <code>Double.NaN</code> then that is the value returned.
   *
   * @param d The specified double
   *
   * @return The lowest double value greater than the specified double.
   */
  public static final double nextDouble (double d)
  {
    return nextDouble (d, true);
  }

  /**
   * This method returns a double that is either the next highest double
   * or next lowest double compared to the specified double depending on the
   * value of the passed boolean parameter.  If the boolean parameter is
   * <code>true</code>, then the lowest possible double greater than the 
   * specified double will be returned.  Otherwise the highest possible
   * double less than the specified double will be returned.
   *
   * @param d The specified double
   * @param positive <code>true</code> to return the next highest
   *                 double, <code>false</code> otherwise. 
   *
   * @return The next highest or lowest double value.
   */
  public static double nextDouble (double d, boolean next)
  {
    if (Double.isInfinite(d) || Double.isNaN(d))
      return d;

    long bits = Double.doubleToLongBits(d);

    long mantMask = (1L << mantissaBits) - 1;
    long mantissa = bits & mantMask;

    long expMask = (1L << exponentBits) - 1;
    long exponent = (bits >>> mantissaBits) & expMask;

    if (next ^ (bits < 0)) // Increment magnitude
      {
	if (mantissa == (1L << mantissaBits) - 1)
	  {
	    mantissa = 0L;
	    exponent++;
	     
	    // Check for absolute overflow.
	    if (exponent >= (1L << mantissaBits))
	      return (bits > 0) ? Double.POSITIVE_INFINITY 
		: Double.NEGATIVE_INFINITY;		      
	  }
	else
	  mantissa++;
      }
    else // Decrement magnitude
      {
	if (exponent == 0L && mantissa == 0L)
	  {
	    // The only case where there is a change of sign
	    return next ? Double.MIN_VALUE : -Double.MIN_VALUE;
	  }
	else
	  {
	    if (mantissa == 0L)
	      {
		mantissa = (1L << mantissaBits) - 1;
		exponent--;
	      }
	    else
	      mantissa--;
	  }
      }

    long result = bits < 0 ? 1 : 0;
    result = (result << exponentBits) | exponent;
    result = (result << mantissaBits) | mantissa;
    return Double.longBitsToDouble(result);
  }

  /**
   * I'm not sure what this method is really supposed to do, as it is
   * not documented.
   */
  public Number parse (String sourceStr, ParsePosition pos)
  {
    int index = pos.getIndex();
    for (int i = 0; i < choiceLimits.length; ++i)
      {
	if (sourceStr.startsWith(choiceFormats[i], index))
	  {
	    pos.setIndex(index + choiceFormats[i].length());
	    return new Double (choiceLimits[i]);
	  }
      }
    pos.setErrorIndex(index);
    return new Double (Double.NaN);
  }

  /**
   * This method returns the highest possible double less than the 
   * specified double.  If the specified double value is equal to
   * <code>Double.NaN</code> then that is the value returned.
   *
   * @param d The specified double
   *
   * @return The highest double value less than the specified double.
   */
  public static final double previousDouble (double d)
  {
    return nextDouble (d, false);
  }

  /**
   * This method sets new range terminators and format strings for this
   * object.
   *
   * @param choiceLimits The new range terminators
   * @param choiceFormats The new choice formats
   */
  public void setChoices (double[] choiceLimits, String[] choiceFormats)
  {
    if (choiceLimits == null || choiceFormats == null)
      throw new NullPointerException ();
    if (choiceLimits.length != choiceFormats.length)
      throw new IllegalArgumentException ();
    this.choiceFormats = (String[]) choiceFormats.clone();
    this.choiceLimits = (double[]) choiceLimits.clone();
  }

  private final void quoteString (StringBuffer dest, String text)
  {
    int max = text.length();
    for (int i = 0; i < max; ++i)
      {
	char c = text.charAt(i);
	if (c == '\'')
	  {
	    dest.append(c);
	    dest.append(c);
	  }
	else if (c == '#' || c == '|' || c == '\u2064' || c == '<')
	  {
	    dest.append('\'');
	    dest.append(c);
	    dest.append('\'');
	  }
	else
	  dest.append(c);
      }
  }

  /**
   * This method returns the range terminator list and format string list
   * as a <code>String</code> suitable for using with the 
   * <code>applyPattern</code> method.
   *
   * @return A pattern string for this object
   */
  public String toPattern ()
  {
    StringBuffer result = new StringBuffer ();
    for (int i = 0; i < choiceLimits.length; ++i)
      {
	result.append(choiceLimits[i]);
	result.append('#');
	quoteString (result, choiceFormats[i]);
      }
    return result.toString();
  }

  /**
   * This is the list of format strings.  Note that this variable is
   * specified by the serialization spec of this class.
   */
  private String[] choiceFormats;

  /**
   * This is the list of range terminator values.  Note that this variable is
   * specified by the serialization spec of this class.
   */
  private double[] choiceLimits;

  // Number of mantissa bits in double.
  private static final int mantissaBits = 52;
  // Number of exponent bits in a double.
  private static final int exponentBits = 11;

  private static final long serialVersionUID = 1795184449645032964L;
}