breakiterator.java

java源代码 请看看啊 提点宝贵的意见

     * @return The first boundary after the specified offset.
     */
    public abstract int following(int offset);

    /**
     * Return the last boundary preceding the specfied offset.
     * The value returned is always less than the offset or the value
     * BreakIterator.DONE.
     * @param offset the offset to begin scanning.  Valid values are
     * determined by the CharacterIterator passed to setText().
     * Invalid values cause an IllegalArgumentException to be thrown.
     * @return The last boundary before the specified offset.
     * @since 1.2
     */
    public int preceding(int offset) {
        // NOTE:  This implementation is here solely because we can't add new
        // abstract methods to an existing class.  There is almost ALWAYS a
        // better, faster way to do this.
        int pos = following(offset);
        while (pos >= offset && pos != DONE)
            pos = previous();
        return pos;
    }

    /**
     * Return true if the specified position is a boundary position.
     * @param offset the offset to check.
     * @return True if "offset" is a boundary position.
     * @since 1.2
     */
    public boolean isBoundary(int offset) {
        // NOTE: This implementation probably is wrong for most situations
        // because it fails to take into account the possibility that a
        // CharacterIterator passed to setText() may not have a begin offset
        // of 0.  But since the abstract BreakIterator doesn't have that
        // knowledge, it assumes the begin offset is 0.  If you subclass
        // BreakIterator, copy the SimpleTextBoundary implementation of this
        // function into your subclass.  [This should have been abstract at
        // this level, but it's too late to fix that now.]
        if (offset == 0)
            return true;
        else
            return following(offset - 1) == offset;
    }

    /**
     * Return character index of the text boundary that was most recently
     * returned by next(), previous(), first(), or last()
     * @return The boundary most recently returned.
     */
    public abstract int current();

    /**
     * Get the text being scanned
     * @return the text being scanned
     */
    public abstract CharacterIterator getText();

    /**
     * Set a new text string to be scanned.  The current scan
     * position is reset to first().
     * @param newText new text to scan.
     */
    public void setText(String newText)
    {
        setText(new StringCharacterIterator(newText));
    }

    /**
     * Set a new text for scanning.  The current scan
     * position is reset to first().
     * @param newText new text to scan.
     */
    public abstract void setText(CharacterIterator newText);

    private static final int CHARACTER_INDEX = 0;
    private static final int WORD_INDEX = 1;
    private static final int LINE_INDEX = 2;
    private static final int SENTENCE_INDEX = 3;
    private static final SoftReference[] iterCache = new SoftReference[4];

    /**
     * Create BreakIterator for word-breaks using default locale.
     * Returns an instance of a BreakIterator implementing word breaks.
     * WordBreak  is usefull for word selection (ex. double click)
     * @return A BreakIterator for word-breaks
     * @see java.util.Locale#getDefault
     */
    public static BreakIterator getWordInstance()
    {
        return getWordInstance(Locale.getDefault());
    }

    /**
     * Create BreakIterator for word-breaks using specified locale.
     * Returns an instance of a BreakIterator implementing word breaks.
     * WordBreak is usefull for word selection (ex. double click)
     * @param where the local.  If a specific WordBreak is not
     * avaliable for the specified locale, a default WordBreak is returned.
     * @return A BreakIterator for word-breaks
     */
    public static BreakIterator getWordInstance(Locale where)
    {
        return getBreakInstance(where,
                                WORD_INDEX,
                                "WordBreakRules",
                                "WordBreakDictionary");
    }

    /**
     * Create BreakIterator for line-breaks using default locale.
     * Returns an instance of a BreakIterator implementing line breaks. Line
     * breaks are logically possible line breaks, actual line breaks are
     * usually determined based on display width.
     * LineBreak is useful for word wrapping text.
     * @return A BreakIterator for line-breaks
     * @see java.util.Locale#getDefault
     */
    public static BreakIterator getLineInstance()
    {
        return getLineInstance(Locale.getDefault());
    }

    /**
     * Create BreakIterator for line-breaks using specified locale.
     * Returns an instance of a BreakIterator implementing line breaks. Line
     * breaks are logically possible line breaks, actual line breaks are
     * usually determined based on display width.
     * LineBreak is useful for word wrapping text.
     * @param where the local.  If a specific LineBreak is not
     * avaliable for the specified locale, a default LineBreak is returned.
     * @return A BreakIterator for line-breaks
     */
    public static BreakIterator getLineInstance(Locale where)
    {
        return getBreakInstance(where,
                                LINE_INDEX,
                                "LineBreakRules",
                                "LineBreakDictionary");
    }

    /**
     * Create BreakIterator for character-breaks using default locale
     * Returns an instance of a BreakIterator implementing character breaks.
     * Character breaks are boundaries of combining character sequences.
     * @return A BreakIterator for character-breaks
     * @see Locale#getDefault
     */
    public static BreakIterator getCharacterInstance()
    {
        return getCharacterInstance(Locale.getDefault());
    }

    /**
     * Create BreakIterator for character-breaks using specified locale
     * Returns an instance of a BreakIterator implementing character breaks.
     * Character breaks are boundaries of combining character sequences.
     * @param where the local.  If a specific character break is not
     * avaliable for the specified local, a default character break is returned.
     * @return A BreakIterator for character-breaks
     */
    public static BreakIterator getCharacterInstance(Locale where)
    {
        return getBreakInstance(where,
                                CHARACTER_INDEX,
                                "CharacterBreakRules",
                                "CharacterBreakDictionary");
    }

    /**
     * Create BreakIterator for sentence-breaks using default locale
     * Returns an instance of a BreakIterator implementing sentence breaks.
     * @return A BreakIterator for sentence-breaks
     * @see java.util.Locale#getDefault
     */
    public static BreakIterator getSentenceInstance()
    {
        return getSentenceInstance(Locale.getDefault());
    }

    /**
     * Create BreakIterator for sentence-breaks using specified locale
     * Returns an instance of a BreakIterator implementing sentence breaks.
     * @param where the local.  If a specific SentenceBreak is not
     * avaliable for the specified local, a default SentenceBreak is returned.
     * @return A BreakIterator for sentence-breaks
     */
    public static BreakIterator getSentenceInstance(Locale where)
    {
        return getBreakInstance(where,
                                SENTENCE_INDEX,
                                "SentenceBreakRules",
                                "SentenceBreakDictionary");
    }

    private static BreakIterator getBreakInstance(Locale where,
                                                  int type,
                                                  String rulesName,
                                                  String dictionaryName) {
        if (iterCache[type] != null) {
            BreakIteratorCache cache = (BreakIteratorCache) iterCache[type].get();
            if (cache != null) {
                if (cache.getLocale().equals(where)) {
                    return cache.createBreakInstance();
                }
            }
        }

        BreakIterator result = createBreakInstance(where,
                                                   type,
                                                   rulesName,
                                                   dictionaryName);
        BreakIteratorCache cache = new BreakIteratorCache(where, result);
        iterCache[type] = new SoftReference(cache);
        return result;
    }

    private static ResourceBundle getBundle(final String baseName, final Locale locale) {
         return (ResourceBundle) AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                return ResourceBundle.getBundle(baseName, locale);
            }
        });
    }

    private static BreakIterator createBreakInstance(Locale where,
                                                     int type,
                                                     String rulesName,
                                                     String dictionaryName) {

        ResourceBundle bundle = getBundle(
                        "sun.text.resources.BreakIteratorRules", where);
        String[] classNames = bundle.getStringArray("BreakIteratorClasses");

        String rules = bundle.getString(rulesName);

        if (classNames[type].equals("RuleBasedBreakIterator")) {
            return new RuleBasedBreakIterator(rules);
        }
        else if (classNames[type].equals("DictionaryBasedBreakIterator")) {
            try {
                URL url = (URL) bundle.getObject(dictionaryName);
                InputStream dictionary = url.openStream();
                return new DictionaryBasedBreakIterator(rules, dictionary);
            }
            catch(IOException e) {
            }
            catch(MissingResourceException e) {
            }
            return new RuleBasedBreakIterator(rules);
        }
        else
            throw new IllegalArgumentException("Invalid break iterator class \"" +
                            classNames[type] + "\"");
    }

    /**
     * Get the set of Locales for which BreakIterators are installed
     * @return available locales
     */
    public static synchronized Locale[] getAvailableLocales()
    {
        //FIX ME - this is a known bug.  It should return
        //all locales.
        return LocaleData.getAvailableLocales("NumberPatterns");
    }

    private static final class BreakIteratorCache {

        private BreakIterator iter;
        private Locale where;

        BreakIteratorCache(Locale where, BreakIterator iter) {
            this.where = where;
            this.iter = (BreakIterator) iter.clone();
        }

        Locale getLocale() {
            return where;
        }

        BreakIterator createBreakInstance() {
            return (BreakIterator) iter.clone();
        }
    }
}