choiceformat.java

来自「《移动Agent技术》一书的所有章节源代码。」· Java 代码 · 共 446 行 · 第 1/2 页

     * @param formats are the formats you want to use for each limit.
     * They can be either Format objects or Strings.
     * When formatting with object Y,
     * if the object is a NumberFormat, then ((NumberFormat) Y).format(X)
     * is called. Otherwise Y.toString() is called.
     */
    public void setChoices(double[] limits, String formats[]) {
        choiceLimits = limits;
        choiceFormats = formats;
    }
    /**
     * Get the limits passed in the constructor.
     * @return the limits.
     */
    public double[] getLimits() {
        return choiceLimits;
    }
    /**
     * Get the formats passed in the constructor.
     * @return the formats.
     */
    public Object[] getFormats() {
        return choiceFormats;
    }

    // Overrides

    /**
     * Specialization of format. This method really calls
     * <code>format(double, StringBuffer, FieldPosition)</code>
     * thus the range of longs that are supported is only equal to
     * the range that can be stored by double. This will never be
     * a practical limitation.
     */
    public StringBuffer format(long number, StringBuffer toAppendTo,
                               FieldPosition status) {
        return format((double)number, toAppendTo, status);
    }

    public StringBuffer format(double number, StringBuffer toAppendTo,
                               FieldPosition status) {
        // find the number
        int i;
        for (i = 0; i < choiceLimits.length; ++i) {
            if (!(number >= choiceLimits[i])) {
                // same as number < choiceLimits, except catchs NaN
                break;
            }
        }
        --i;
        if (i < 0) i = 0;
        // return either a formatted number, or a string
        return toAppendTo.append(choiceFormats[i]);
    }

    public Number parse(String text, ParsePosition status) {
        // find the best number (defined as the one with the longest parse)
        int start = status.index;
        int furthest = start;
        double bestNumber = Double.NaN;
        double tempNumber = 0.0;
        for (int i = 0; i < choiceFormats.length; ++i) {
            String tempString = choiceFormats[i];
            if (text.regionMatches(start, tempString, 0, tempString.length())) {
                status.index = tempString.length();
                tempNumber = choiceLimits[i];
                if (status.index > furthest) {
                    furthest = status.index;
                    bestNumber = tempNumber;
                    if (furthest == text.length()) break;
                }
            }
        }
        status.index = furthest;
        return new Double(bestNumber);
    }

    /**
     * Finds the least double greater than d.
     * If NaN, returns same value.
     * <p>Used to make half-open intervals.
     * @see #previousDouble
     */
    public static final double nextDouble (double d) {
        return nextDouble(d,true);
    }

    /**
     * Finds the greatest double less than d.
     * If NaN, returns same value.
     * @see #nextDouble
     */
    public static final double previousDouble (double d) {
        return nextDouble(d,false);
    }

    /**
     * Overrides Cloneable
     */
    public Object clone()
    {
        ChoiceFormat other = (ChoiceFormat) super.clone();
        // for primitives or immutables, shallow clone is enough
        other.choiceLimits = (double[]) choiceLimits.clone();
        other.choiceFormats = (String[]) choiceFormats.clone();
        return other;
    }

    /**
     * Generates a hash code for the message format object.
     */
    public int hashCode() {
        int result = choiceLimits.length;
        if (choiceFormats.length > 0) {
            // enough for reasonable distribution
            result ^= choiceFormats[choiceFormats.length-1].hashCode();
        }
        return result;
    }

    /**
     * Equality comparision between two
     */
    public boolean equals(Object obj) {
        if (this == obj)                      // quick check
            return true;
        if (getClass() != obj.getClass())
            return false;
        ChoiceFormat other = (ChoiceFormat) obj;
        return (Utility.arrayEquals(choiceLimits,other.choiceLimits)
        	&& Utility.arrayEquals(choiceFormats,other.choiceFormats));
    }
    // ===============privates===========================
    private double[] choiceLimits;
    private String[] choiceFormats;

    /*
    static final long SIGN          = 0x8000000000000000L;
    static final long EXPONENT      = 0x7FF0000000000000L;
    static final long SIGNIFICAND   = 0x000FFFFFFFFFFFFFL;

    private static double nextDouble (double d, boolean positive) {
        if (Double.isNaN(d) || Double.isInfinite(d)) {
                return d;
            }
        long bits = Double.doubleToLongBits(d);
        long significand = bits & SIGNIFICAND;
        if (bits < 0) {
            significand |= (SIGN | EXPONENT);
        }
        long exponent = bits & EXPONENT;
        if (positive) {
            significand += 1;
            // FIXME fix overflow & underflow
        } else {
            significand -= 1;
            // FIXME fix overflow & underflow
        }
        bits = exponent | (significand & ~EXPONENT);
        return Double.longBitsToDouble(bits);
    }
    */

    /*
     * Finds the least double greater than d (if positive == true),
     * or the greatest double less than d (if positive == false).
     * If NaN, returns same value.
     *
     * Does not affect floating-point flags,
     *  provided these member functions do not:
     *          Double.longBitsToDouble ()
     *          Double.doubleToLongBits ()
     *          Double.IsNaN ()
     */

    static final long SIGN                = 0x8000000000000000L;
    static final long EXPONENT            = 0x7FF0000000000000L;
    static final long POSITIVEINFINITY    = 0x7FF0000000000000L;

    public static double nextDouble (double d, boolean positive) {

        /* filter out NaN's */
        if (Double.isNaN(d)) {
            return d;
        }

        /* zero's are also a special case */
        if (d == 0.0) {
            double smallestPositiveDouble = Double.longBitsToDouble(1L);
            if (positive) {
                return smallestPositiveDouble;
            } else {
                return -smallestPositiveDouble;
            }
        }

        /* if entering here, d is a nonzero value */

        /* hold all bits in a long for later use */
        long bits = Double.doubleToLongBits(d);

        /* strip off the sign bit */
        long magnitude = bits & ~SIGN;

        /* if next double away from zero, increase magnitude */
        if ((bits > 0) == positive) {
            if (magnitude != POSITIVEINFINITY) {
                magnitude += 1;
            }
        }
        /* else decrease magnitude */
        else {
            magnitude -= 1;
        }

        /* restore sign bit and return */
        long signbit = bits & SIGN;
        return Double.longBitsToDouble (magnitude | signbit);
    }

}