decimalformat.java

java源代码 请看看啊 提点宝贵的意见

 *         if (locales[i].getCountry().length() == 0) {
 *            continue; // Skip language-only locales
 *         }
 *         System.out.print(locales[i].getDisplayName());
 *         switch (j) {
 *         case 0:
 *             form = NumberFormat.getInstance(locales[i]); break;
 *         case 1:
 *             form = NumberFormat.getIntegerInstance(locales[i]); break;
 *         case 2:
 *             form = NumberFormat.getCurrencyInstance(locales[i]); break;
 *         default:
 *             form = NumberFormat.getPercentInstance(locales[i]); break;
 *         }
 *         if (form instanceof DecimalFormat) {
 *             System.out.print(": " + ((DecimalFormat) form).toPattern());
 *         }
 *         System.out.print(" -> " + form.format(myNumber));
 *         try {
 *             System.out.println(" -> " + form.parse(form.format(myNumber)));
 *         } catch (ParseException e) {}
 *     }
 * }
 * </pre></blockquote>
 *
 * @see          <a href="http://java.sun.com/docs/books/tutorial/i18n/format/decimalFormat.html">Java Tutorial</a>
 * @see          NumberFormat
 * @see          DecimalFormatSymbols
 * @see          ParsePosition
 * @version      1.71 01/23/03
 * @author       Mark Davis
 * @author       Alan Liu
 */
public class DecimalFormat extends NumberFormat {

    /**
     * Creates a DecimalFormat using the default pattern and symbols
     * for the default locale. This is a convenient way to obtain a
     * DecimalFormat when internationalization is not the main concern.
     * <p>
     * To obtain standard formats for a given locale, use the factory methods
     * on NumberFormat such as getNumberInstance. These factories will
     * return the most appropriate sub-class of NumberFormat for a given
     * locale.
     *
     * @see java.text.NumberFormat#getInstance
     * @see java.text.NumberFormat#getNumberInstance
     * @see java.text.NumberFormat#getCurrencyInstance
     * @see java.text.NumberFormat#getPercentInstance
     */
    public DecimalFormat() {
        Locale def = Locale.getDefault();
        // try to get the pattern from the cache
        String pattern = (String) cachedLocaleData.get(def);
        if (pattern == null) {  /* cache miss */
            // Get the pattern for the default locale.
            ResourceBundle rb = LocaleData.getLocaleElements(def);
            String[] all = rb.getStringArray("NumberPatterns");
            pattern = all[0];
            /* update cache */
            cachedLocaleData.put(def, pattern);
        }

        // Always applyPattern after the symbols are set
        this.symbols = new DecimalFormatSymbols(def);
        applyPattern(pattern, false);
    }


    /**
     * Creates a DecimalFormat using the given pattern and the symbols
     * for the default locale. This is a convenient way to obtain a
     * DecimalFormat when internationalization is not the main concern.
     * <p>
     * To obtain standard formats for a given locale, use the factory methods
     * on NumberFormat such as getNumberInstance. These factories will
     * return the most appropriate sub-class of NumberFormat for a given
     * locale.
     *
     * @param pattern A non-localized pattern string.
     * @exception NullPointerException if <code>pattern</code> is null
     * @exception IllegalArgumentException if the given pattern is invalid.
     * @see java.text.NumberFormat#getInstance
     * @see java.text.NumberFormat#getNumberInstance
     * @see java.text.NumberFormat#getCurrencyInstance
     * @see java.text.NumberFormat#getPercentInstance
     */
    public DecimalFormat(String pattern) {
        // Always applyPattern after the symbols are set
        this.symbols = new DecimalFormatSymbols(Locale.getDefault());
        applyPattern(pattern, false);
    }


    /**
     * Creates a DecimalFormat using the given pattern and symbols.
     * Use this constructor when you need to completely customize the
     * behavior of the format.
     * <p>
     * To obtain standard formats for a given
     * locale, use the factory methods on NumberFormat such as
     * getInstance or getCurrencyInstance. If you need only minor adjustments
     * to a standard format, you can modify the format returned by
     * a NumberFormat factory method.
     *
     * @param pattern a non-localized pattern string
     * @param symbols the set of symbols to be used
     * @exception NullPointerException if any of the given arguments is null
     * @exception IllegalArgumentException if the given pattern is invalid
     * @see java.text.NumberFormat#getInstance
     * @see java.text.NumberFormat#getNumberInstance
     * @see java.text.NumberFormat#getCurrencyInstance
     * @see java.text.NumberFormat#getPercentInstance
     * @see java.text.DecimalFormatSymbols
     */
    public DecimalFormat (String pattern, DecimalFormatSymbols symbols) {
        // Always applyPattern after the symbols are set
        this.symbols = (DecimalFormatSymbols)symbols.clone();
        applyPattern(pattern, false);
    }


    // Overrides
    /**
     * Formats a double to produce a string.
     * @param number    The double to format
     * @param result    where the text is to be appended
     * @param fieldPosition    On input: an alignment field, if desired.
     * On output: the offsets of the alignment field.
     * @return The formatted number string
     * @see java.text.FieldPosition
     */
    public StringBuffer format(double number, StringBuffer result,
                               FieldPosition fieldPosition)
    {
        fieldPosition.setBeginIndex(0);
        fieldPosition.setEndIndex(0);
        return format(number, result, fieldPosition.getFieldDelegate());
    }

    /**
     * Formats a double to produce a string.
     * @param number    The double to format
     * @param result    where the text is to be appended
     * @param delegate notified of locations of sub fields
     * @return The formatted number string
     */
    private StringBuffer format(double number, StringBuffer result,
                                FieldDelegate delegate) {
        if (Double.isNaN(number))
        {
            int iFieldStart = result.length();

            result.append(symbols.getNaN());

            delegate.formatted(INTEGER_FIELD, Field.INTEGER, Field.INTEGER,
                               iFieldStart, result.length(), result);
            return result;
        }

        /* Detecting whether a double is negative is easy with the exception of
         * the value -0.0.  This is a double which has a zero mantissa (and
         * exponent), but a negative sign bit.  It is semantically distinct from
         * a zero with a positive sign bit, and this distinction is important
         * to certain kinds of computations.  However, it's a little tricky to
         * detect, since (-0.0 == 0.0) and !(-0.0 < 0.0).  How then, you may
         * ask, does it behave distinctly from +0.0?  Well, 1/(-0.0) ==
         * -Infinity.  Proper detection of -0.0 is needed to deal with the
         * issues raised by bugs 4106658, 4106667, and 4147706.  Liu 7/6/98.
         */
        boolean isNegative = (number < 0.0) || (number == 0.0 && 1/number < 0.0);
        if (isNegative) number = -number;

        // Do this BEFORE checking to see if value is infinite!
        if (multiplier != 1) number *= multiplier;

        if (Double.isInfinite(number))
        {
            if (isNegative) {
                append(result, negativePrefix, delegate,
                       getNegativePrefixFieldPositions(), Field.SIGN);
            }
            else {
                append(result, positivePrefix, delegate,
                       getPositivePrefixFieldPositions(), Field.SIGN);
            }
            int iFieldStart = result.length();

            result.append(symbols.getInfinity());

            delegate.formatted(INTEGER_FIELD, Field.INTEGER, Field.INTEGER,
                               iFieldStart, result.length(), result);

            if (isNegative) {
                append(result, negativeSuffix, delegate,
                       getNegativeSuffixFieldPositions(), Field.SIGN);
            }
            else {
                append(result, positiveSuffix, delegate,
                       getPositiveSuffixFieldPositions(), Field.SIGN);
            }
            return result;
        }

        // At this point we are guaranteed a nonnegative finite
        // number.
        synchronized(digitList) {
            digitList.set(number, useExponentialNotation ?
                      getMaximumIntegerDigits() + getMaximumFractionDigits() :
                      getMaximumFractionDigits(),
                      !useExponentialNotation);

            return subformat(result, delegate, isNegative, false);
        }
    }

    /**
     * Format a long to produce a string.
     * @param number    The long to format
     * @param result    where the text is to be appended
     * @param fieldPosition    On input: an alignment field, if desired.
     * On output: the offsets of the alignment field.
     * @return The formatted number string
     * @see java.text.FieldPosition
     */
    public StringBuffer format(long number, StringBuffer result,
                               FieldPosition fieldPosition)
    {
        fieldPosition.setBeginIndex(0);
        fieldPosition.setEndIndex(0);

        return format(number, result, fieldPosition.getFieldDelegate());
    }


    /**
     * Format a long to produce a string.
     * @param number    The long to format
     * @param result    where the text is to be appended
     * @param delegate notified of locations of sub fields
     * @return The formatted number string
     * @see java.text.FieldPosition
     */
    private StringBuffer format(long number, StringBuffer result,
                               FieldDelegate delegate) {
        boolean isNegative = (number < 0);
        if (isNegative) number = -number;

        // In general, long values always represent real finite numbers, so
        // we don't have to check for +/- Infinity or NaN.  However, there
        // is one case we have to be careful of:  The multiplier can push
        // a number near MIN_VALUE or MAX_VALUE outside the legal range.  We
        // check for this before multiplying, and if it happens we use doubles
        // instead, trading off accuracy for range.
        if (multiplier != 1 && multiplier != 0)
        {
            boolean useDouble = false;

            if (number < 0) // This can only happen if number == Long.MIN_VALUE
            {
                long cutoff = Long.MIN_VALUE / multiplier;
                useDouble = (number < cutoff);
            }
            else
            {
                long cutoff = Long.MAX_VALUE / multiplier;
                useDouble = (number > cutoff);
            }

            if (useDouble)
            {
                double dnumber = (double)(isNegative ? -number : number);
                return format(dnumber, result, delegate);
            }
        }

        number *= multiplier;
        synchronized(digitList) {
            digitList.set(number, useExponentialNotation ?
                      getMaximumIntegerDigits() + getMaximumFractionDigits() : 0);

            return subformat(result, delegate, isNegative, true);
        }
    }

    /**
     * Formats an Object producing an <code>AttributedCharacterIterator</code>.
     * You can use the returned <code>AttributedCharacterIterator</code>
     * to build the resulting String, as well as to determine information
     * about the resulting String.
     * <p>
     * Each attribute key of the AttributedCharacterIterator will be of type
     * <code>NumberFormat.Field</code>, with the attribute value being the
     * same as the attribute key.
     *
     * @exception NullPointerException if obj is null.
     * @exception IllegalArgumentException when the Format cannot format the
     *            given object.
     * @param obj The object to format
     * @return AttributedCharacterIterator describing the formatted value.
     * @since 1.4
     */
    public AttributedCharacterIterator formatToCharacterIterator(Object obj) {
        CharacterIteratorFieldDelegate delegate =
                         new CharacterIteratorFieldDelegate();
        StringBuffer sb = new StringBuffer();

        if (obj instanceof Long ||
            (obj instanceof BigInteger &&
             ((BigInteger)obj).bitLength() < 64)) {
            format(((Number)obj).longValue(), sb, delegate);
        }
        else if (obj == null) {
            throw new NullPointerException(
                   "formatToCharacterIterator must be passed non-null object");
        }