BreakIterator class implements methods for finding
* the location of boundaries in text. Instances of BreakIterator
* maintain a current position and scan over text
* returning the index of characters where boundaries occur.
* Internally, BreakIterator scans text using a
* CharacterIterator, and is thus able to scan text held
* by any object implementing that protocol. A StringCharacterIterator
* is used to scan String objects passed to setText.
*
*
* You use the factory methods provided by this class to create
* instances of various types of break iterators. In particular,
* use getWordIterator, getLineIterator,
* getSentenceIterator, and getCharacterIterator
* to create BreakIterators that perform
* word, line, sentence, and character boundary analysis respectively.
* A single BreakIterator can work only on one unit
* (word, line, sentence, and so on). You must use a different iterator
* for each unit boundary analysis you wish to perform.
*
*
* Line boundary analysis determines where a text string can be * broken when line-wrapping. The mechanism correctly handles * punctuation and hyphenated words. * *
* Sentence boundary analysis allows selection with correct interpretation * of periods within numbers and abbreviations, and trailing punctuation * marks such as quotation marks and parentheses. * *
* Word boundary analysis is used by search and replace functions, as * well as within text editing applications that allow the user to * select words with a double click. Word selection provides correct * interpretation of punctuation marks within and following * words. Characters that are not part of a word, such as symbols * or punctuation marks, have word-breaks on both sides. * *
* Character boundary analysis allows users to interact with characters * as they expect to, for example, when moving the cursor through a text * string. Character boundary analysis provides correct navigation of * through character strings, regardless of how the character is stored. * For example, an accented character might be stored as a base character * and a diacritical mark. What users consider to be a character can * differ between languages. * *
* BreakIterator is intended for use with natural
* languages only. Do not use this class to tokenize a programming language.
*
*
* Examples:
* Creating and using text boundaries *
*
* public static void main(String args[]) {
* if (args.length == 1) {
* String stringToExamine = args[0];
* //print each word in order
* BreakIterator boundary = BreakIterator.getWordInstance();
* boundary.setText(stringToExamine);
* printEachForward(boundary, stringToExamine);
* //print each sentence in reverse order
* boundary = BreakIterator.getSentenceInstance(Locale.US);
* boundary.setText(stringToExamine);
* printEachBackward(boundary, stringToExamine);
* printFirst(boundary, stringToExamine);
* printLast(boundary, stringToExamine);
* }
* }
*
*
*
* Print each element in order
*
*
* public static void printEachForward(BreakIterator boundary, String source) {
* int start = boundary.first();
* for (int end = boundary.next();
* end != BreakIterator.DONE;
* start = end, end = boundary.next()) {
* System.out.println(source.substring(start,end));
* }
* }
*
*
*
* Print each element in reverse order
*
*
* public static void printEachBackward(BreakIterator boundary, String source) {
* int end = boundary.last();
* for (int start = boundary.previous();
* start != BreakIterator.DONE;
* end = start, start = boundary.previous()) {
* System.out.println(source.substring(start,end));
* }
* }
*
*
*
* Print first element
*
*
* public static void printFirst(BreakIterator boundary, String source) {
* int start = boundary.first();
* int end = boundary.next();
* System.out.println(source.substring(start,end));
* }
*
*
*
* Print last element
*
*
* public static void printLast(BreakIterator boundary, String source) {
* int end = boundary.last();
* int start = boundary.previous();
* System.out.println(source.substring(start,end));
* }
*
*
*
* Print the element at a specified position
*
*
* public static void printAt(BreakIterator boundary, int pos, String source) {
* int end = boundary.following(pos);
* int start = boundary.previous();
* System.out.println(source.substring(start,end));
* }
*
*
*
* Find the next word
*
*
* public static int nextWordStartAfter(int pos, String text) {
* BreakIterator wb = BreakIterator.getWordInstance();
* wb.setText(text);
* int last = wb.following(pos);
* int current = wb.next();
* while (current != BreakIterator.DONE) {
* for (int p = last; p < current; p++) {
* if (Character.isLetter(text.codePointAt(p))
* return last;
* }
* last = current;
* current = wb.next();
* }
* return BreakIterator.DONE;
* }
*
* (The iterator returned by BreakIterator.getWordInstance() is unique in that
* the break positions it returns don't represent both the start and end of the
* thing being iterated over. That is, a sentence-break iterator returns breaks
* that each represent the end of one sentence and the beginning of the next.
* With the word-break iterator, the characters between two boundaries might be a
* word, or they might be the punctuation or whitespace between two words. The
* above code uses a simple heuristic to determine which boundary is the beginning
* of a word: If the characters between this boundary and the next boundary
* include at least one letter (this can be an alphabetical letter, a CJK ideograph,
* a Hangul syllable, a Kana character, etc.), then the text between this boundary
* and the next is a word; otherwise, it's the material between words.)
*
*
* @see CharacterIterator
*
*/
public abstract class BreakIterator implements Cloneable
{
/**
* Constructor. BreakIterator is stateless and has no default behavior.
*/
protected BreakIterator()
{
}
/**
* Create a copy of this iterator
* @return A copy of this
*/
public Object clone()
{
try {
return super.clone();
}
catch (CloneNotSupportedException e) {
throw new InternalError();
}
}
/**
* DONE is returned by previous() and next() after all valid
* boundaries have been returned.
*/
public static final int DONE = -1;
/**
* Return the first boundary. The iterator's current position is set
* to the first boundary.
* @return The character index of the first text boundary.
*/
public abstract int first();
/**
* Return the last boundary. The iterator's current position is set
* to the last boundary.
* @return The character index of the last text boundary.
*/
public abstract int last();
/**
* Return the nth boundary from the current boundary
* @param n which boundary to return. A value of 0
* does nothing. Negative values move to previous boundaries
* and positive values move to later boundaries.
* @return The index of the nth boundary from the current position.
*/
public abstract int next(int n);
/**
* Return the boundary following the current boundary.
* @return The character index of the next text boundary or DONE if all
* boundaries have been returned. Equivalent to next(1).
*/
public abstract int next();
/**
* Return the boundary preceding the current boundary.
* @return The character index of the previous text boundary or DONE if all
* boundaries have been returned.
*/
public abstract int previous();
/**
* Return the first boundary following the specified offset.
* The value returned is always greater 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 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,
"WordData",
"WordDictionary");
}
/**
* 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,
"LineData",
"LineDictionary");
}
/**
* 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,
"CharacterData",
"CharacterDictionary");
}
/**
* 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,
"SentenceData",
"SentenceDictionary");
}
private static BreakIterator getBreakInstance(Locale where,
int type,
String dataName,
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,
dataName,
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 dataName,
String dictionaryName) {
ResourceBundle bundle = getBundle(
"sun.text.resources.BreakIteratorInfo", where);
String[] classNames = bundle.getStringArray("BreakIteratorClasses");
String dataFile = bundle.getString(dataName);
try {
if (classNames[type].equals("RuleBasedBreakIterator")) {
return new RuleBasedBreakIterator(dataFile);
}
else if (classNames[type].equals("DictionaryBasedBreakIterator")) {
String dictionaryFile = bundle.getString(dictionaryName);
return new DictionaryBasedBreakIterator(dataFile, dictionaryFile);
}
else {
throw new IllegalArgumentException("Invalid break iterator class \"" +
classNames[type] + "\"");
}
}
catch (Exception e) {
throw new InternalError(e.toString());
}
}
/**
* Returns an array of all locales for which the
* get*Instance methods of this class can return
* localized instances.
* The array returned must contain at least a Locale
* instance equal to {@link java.util.Locale#US Locale.US}.
*
* @return An array of locales for which localized
* BreakIterator instances are available.
*/
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();
}
}
protected static long getLong(byte[] buf, int offset) {
long num = buf[offset]&0xFF;
for (int i = 1; i < 8; i++) {
num = num<<8 | (buf[offset+i]&0xFF);
}
return num;
}
protected static int getInt(byte[] buf, int offset) {
int num = buf[offset]&0xFF;
for (int i = 1; i < 4; i++) {
num = num<<8 | (buf[offset+i]&0xFF);
}
return num;
}
protected static short getShort(byte[] buf, int offset) {
short num = (short)(buf[offset]&0xFF);
num = (short)(num<<8 | (buf[offset+1]&0xFF));
return num;
}
}