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/*
*******************************************************************************
* Copyright (C) 1996-2000, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*
* $Source: /xsrl/Nsvn/icu/icu4j/src/com/ibm/icu/text/BreakIterator.java,v $
* $Date: 2002/12/05 01:21:28 $
* $Revision: 1.13 $
*
*****************************************************************************************
*/
package com.ibm.icu.text;
import com.ibm.icu.impl.ICULocaleData;
import com.ibm.icu.impl.ICULocaleService;
import com.ibm.icu.impl.ICULocaleService.LocaleKey;
import com.ibm.icu.impl.ICULocaleService.ICUResourceBundleFactory;
import com.ibm.icu.impl.ICUService;
import com.ibm.icu.impl.ICUService.Factory;
import com.ibm.icu.impl.ICUService.Key;
import com.ibm.icu.impl.LocaleUtility;
import java.io.InputStream;
import java.io.IOException;
import java.lang.ref.SoftReference;
import java.net.URL;
import java.text.CharacterIterator;
import java.text.StringCharacterIterator;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
import java.util.Vector;
/**
* A class that locates boundaries in text. This class defines a protocol for
* objects that break up a piece of natural-language text according to a set
* of criteria. Instances or subclasses of BreakIterator can be provided, for
* example, to break a piece of text into words, sentences, or logical characters
* according to the conventions of some language or group of languages.
*
* We provide four built-in types of BreakIterator:
* <ul><li>getSentenceInstance() returns a BreakIterator that locates boundaries
* between sentences. This is useful for triple-click selection, for example.
* <li>getWordInstance() returns a BreakIterator that locates boundaries between
* words. This is useful for double-click selection or "find whole words" searches.
* This type of BreakIterator makes sure there is a boundary position at the
* beginning and end of each legal word. (Numbers count as words, too.) Whitespace
* and punctuation are kept separate from real words.
* <li>getLineInstance() returns a BreakIterator that locates positions where it is
* legal for a text editor to wrap lines. This is similar to word breaking, but
* not the same: punctuation and whitespace are generally kept with words (you don't
* want a line to start with whitespace, for example), and some special characters
* can force a position to be considered a line-break position or prevent a position
* from being a line-break position.
* <li>getCharacterInstance() returns a BreakIterator that locates boundaries between
* logical characters. Because of the structure of the Unicode encoding, a logical
* character may be stored internally as more than one Unicode code point. (A with an
* umlaut may be stored as an a followed by a separate combining umlaut character,
* for example, but the user still thinks of it as one character.) This iterator allows
* various processes (especially text editors) to treat as characters the units of text
* that a user would think of as characters, rather than the units of text that the
* computer sees as "characters".</ul>
*
* BreakIterator's interface follows an "iterator" model (hence the name), meaning it
* has a concept of a "current position" and methods like first(), last(), next(),
* and previous() that update the current position. All BreakIterators uphold the
* following invariants:
* <ul><li>The beginning and end of the text are always treated as boundary positions.
* <li>The current position of the iterator is always a boundary position (random-
* access methods move the iterator to the nearest boundary position before or
* after the specified position, not _to_ the specified position).
* <li>DONE is used as a flag to indicate when iteration has stopped. DONE is only
* returned when the current position is the end of the text and the user calls next(),
* or when the current position is the beginning of the text and the user calls
* previous().
* <li>Break positions are numbered by the positions of the characters that follow
* them. Thus, under normal circumstances, the position before the first character
* is 0, the position after the first character is 1, and the position after the
* last character is 1 plus the length of the string.
* <li>The client can change the position of an iterator, or the text it analyzes,
* at will, but cannot change the behavior. If the user wants different behavior, he
* must instantiate a new iterator.</ul>
*
* BreakIterator accesses the text it analyzes through a CharacterIterator, which makes
* it possible to use BreakIterator to analyze text in any text-storage vehicle that
* provides a CharacterIterator interface.
*
* <b>NOTE:</b> Some types of BreakIterator can take a long time to create, and
* instances of BreakIterator are not currently cached by the system. For
* optimal performance, keep instances of BreakIterator around as long as makes
* sense. For example, when word-wrapping a document, don't create and destroy a
* new BreakIterator for each line. Create one break iterator for the whole document
* (or whatever stretch of text you're wrapping) and use it to do the whole job of
* wrapping the text.
*
* <P>
* <strong>Examples</strong>:<P>
* Creating and using text boundaries
* <blockquote>
* <pre>
* 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);
* }
* }
* </pre>
* </blockquote>
*
* Print each element in order
* <blockquote>
* <pre>
* 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));
* }
* }
* </pre>
* </blockquote>
*
* Print each element in reverse order
* <blockquote>
* <pre>
* 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));
* }
* }
* </pre>
* </blockquote>
*
* Print first element
* <blockquote>
* <pre>
* public static void printFirst(BreakIterator boundary, String source) {
* int start = boundary.first();
* int end = boundary.next();
* System.out.println(source.substring(start,end));
* }
* </pre>
* </blockquote>
*
* Print last element
* <blockquote>
* <pre>
* public static void printLast(BreakIterator boundary, String source) {
* int end = boundary.last();
* int start = boundary.previous();
* System.out.println(source.substring(start,end));
* }
* </pre>
* </blockquote>
*
* Print the element at a specified position
* <blockquote>
* <pre>
* 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));
* }
* </pre>
* </blockquote>
*
* Find the next word
* <blockquote>
* <pre>
* 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.charAt(p))
* return last;
* }
* last = current;
* current = wb.next();
* }
* return BreakIterator.DONE;
* }
* </pre>
* (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.)
* </blockquote>
*
* @see CharacterIterator
* @stable ICU 2.0
*
*/
public abstract class BreakIterator implements Cloneable
{
/**
* Default constructor. There is no state that is carried by this abstract
* base class.
* @stable ICU 2.0
*/
protected BreakIterator()
{
}
/**
* Clone method. Creates another BreakIterator with the same behavior and
* current state as this one.
* @return The clone.
* @stable ICU 2.0
*/
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.
* @stable ICU 2.0
*/
public static final int DONE = -1;
/**
* Return the first boundary position. This is always the beginning
* index of the text this iterator iterates over. For example, if
* the iterator iterates over a whole string, this function will
* always return 0. This function also updates the iteration position
* to point to the beginning of the text.
* @return The character offset of the beginning of the stretch of text
* being broken.
* @stable ICU 2.0
*/
public abstract int first();
/**
* Return the last boundary position. This is always the "past-the-end"
* index of the text this iterator iterates over. For example, if the
* iterator iterates over a whole string (call it "text"), this function
* will always return text.length(). This function also updated the
* iteration position to point to the end of the text.
* @return The character offset of the end of the stretch of text
* being broken.
* @stable ICU 2.0
*/
public abstract int last();
/**
* Advances the specified number of steps forward in the text (a negative
* number, therefore, advances backwards). If this causes the iterator
* to advance off either end of the text, this function returns DONE;
* otherwise, this function returns the position of the appropriate
* boundary. Calling this function is equivalent to calling next() or
* previous() n times.
* @param n The number of boundaries to advance over (if positive, moves
* forward; if negative, moves backwards).
* @return The position of the boundary n boundaries from the current
* iteration position, or DONE if moving n boundaries causes the iterator
* to advance off either end of the text.
* @stable ICU 2.0
*/
public abstract int next(int n);
/**
* Advances the iterator forward one boundary. The current iteration
* position is updated to point to the next boundary position after the
* current position, and this is also the value that is returned. If
* the current position is equal to the value returned by last(), or to
* DONE, this function returns DONE and sets the current position to
* DONE.
* @return The position of the first boundary position following the
* iteration position.
* @stable ICU 2.0
*/
public abstract int next();
/**
* Advances the iterator backward one boundary. The current iteration
* position is updated to point to the last boundary position before
* the current position, and this is also the value that is returned. If
* the current position is equal to the value returned by first(), or to
* DONE, this function returns DONE and sets the current position to
* DONE.
* @return The position of the last boundary position preceding the
* iteration position.
* @stable ICU 2.0
*/
public abstract int previous();
/**
* Sets the iterator's current iteration position to be the first
* boundary position following the specified position. (Whether the
* specified position is itself a boundary position or not doesn't
* matter-- this function always moves the iteration position to the
* first boundary after the specified position.) If the specified
* position is the past-the-end position, returns DONE.
* @param offset The character position to start searching from.
* @return The position of the first boundary position following
* "offset" (whether or not "offset" itself is a boundary position),
* or DONE if "offset" is the past-the-end offset.
* @stable ICU 2.0
*/
public abstract int following(int offset);
/**
* Sets the iterator's current iteration position to be the last
* boundary position preceding the specified position. (Whether the
* specified position is itself a boundary position or not doesn't
* matter-- this function always moves the iteration position to the
* last boundary before the specified position.) If the specified
* position is the starting position, returns DONE.
* @param offset The character position to start searching from.
* @return The position of the last boundary position preceding
* "offset" (whether of not "offset" itself is a boundary position),
* or DONE if "offset" is the starting offset of the iterator.
* @stable ICU 2.0
*/
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 specfied position is a boundary position. If the
* function returns true, the current iteration position is set to the
* specified position; if the function returns false, the current
* iteration position is set as though following() had been called.
* @param offset the offset to check.
* @return True if "offset" is a boundary position.
* @stable ICU 2.0
*/
public boolean isBoundary(int offset) {
// Again, this is the default implementation, which is provided solely because
// we couldn't add a new abstract method to an existing class. The real
// implementations will usually need to do a little more work.
if (offset == 0) {
return true;
}
else
return following(offset - 1) == offset;
}
/**
* Return the iterator's current position.
* @return The iterator's current position.
* @stable ICU 2.0
*/
public abstract int current();
/**
* Returns a CharacterIterator over the text being analyzed.
* For at least some subclasses of BreakIterator, this is a reference
* to the <b>actual iterator being used</b> by the BreakIterator,
* and therefore, this function's return value should be treated as
* <tt>const</tt>. No guarantees are made about the current position
* of this iterator when it is returned. If you need to move that
* position to examine the text, clone this function's return value first.
* @return A CharacterIterator over the text being analyzed.
* @stable ICU 2.0
*/
public abstract CharacterIterator getText();
/**
* Sets the iterator to analyze a new piece of text. The new
* piece of text is passed in as a String, and the current
* iteration position is reset to the beginning of the string.
* (The old text is dropped.)
* @param newText A String containing the text to analyze with
* this BreakIterator.
* @stable ICU 2.0
*/
public void setText(String newText)
{
setText(new StringCharacterIterator(newText));
}
/**
* Sets the iterator to analyze a new piece of text. The
* BreakIterator is passed a CharacterIterator through which
* it will access the text itself. The current iteration
* position is reset to the CharacterIterator's start index.
* (The old iterator is dropped.)
* @param newText A CharacterIterator referring to the text
* to analyze with this BreakIterator (the iterator's current
* position is ignored, but its other state is significant).
* @stable ICU 2.0
*/
public abstract void setText(CharacterIterator newText);
/** @stable ICU 2.0 */
public static final int KIND_CHARACTER = 0;
/** @stable ICU 2.0 */
public static final int KIND_WORD = 1;
/** @stable ICU 2.0 */
public static final int KIND_LINE = 2;
/** @stable ICU 2.0 */
public static final int KIND_SENTENCE = 3;
/** @stable ICU 2.0 */
public static final int KIND_TITLE = 4;
/*
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 int TITLE_INDEX = 4;
*/
/** @internal */
private static final SoftReference[] iterCache = new SoftReference[5];
/**
* Returns a new instance of BreakIterator that locates word boundaries.
* This function assumes that the text being analyzed is in the default
* locale's language.
* @return An instance of BreakIterator that locates word boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getWordInstance()
{
return getWordInstance(Locale.getDefault());
}
/**
* Returns a new instance of BreakIterator that locates word boundaries.
* @param where A locale specifying the language of the text to be
* analyzed.
* @return An instance of BreakIterator that locates word boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getWordInstance(Locale where)
{
return getBreakInstance(where, KIND_WORD);
}
/**
* Returns a new instance of BreakIterator that locates legal line-
* wrapping positions. This function assumes the text being broken
* is in the default locale's language.
* @return A new instance of BreakIterator that locates legal
* line-wrapping positions.
* @stable ICU 2.0
*/
public static BreakIterator getLineInstance()
{
return getLineInstance(Locale.getDefault());
}
/**
* Returns a new instance of BreakIterator that locates legal line-
* wrapping positions.
* @param where A Locale specifying the language of the text being broken.
* @return A new instance of BreakIterator that locates legal
* line-wrapping positions.
* @stable ICU 2.0
*/
public static BreakIterator getLineInstance(Locale where)
{
return getBreakInstance(where, KIND_LINE);
}
/**
* Returns a new instance of BreakIterator that locates logical-character
* boundaries. This function assumes that the text being analyzed is
* in the default locale's language.
* @return A new instance of BreakIterator that locates logical-character
* boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getCharacterInstance()
{
return getCharacterInstance(Locale.getDefault());
}
/**
* Returns a new instance of BreakIterator that locates logical-character
* boundaries.
* @param where A Locale specifying the language of the text being analyzed.
* @return A new instance of BreakIterator that locates logical-character
* boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getCharacterInstance(Locale where)
{
return getBreakInstance(where, KIND_CHARACTER);
}
/**
* Returns a new instance of BreakIterator that locates sentence boundaries.
* This function assumes the text being analyzed is in the default locale's
* language.
* @return A new instance of BreakIterator that locates sentence boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getSentenceInstance()
{
return getSentenceInstance(Locale.getDefault());
}
/**
* Returns a new instance of BreakIterator that locates sentence boundaries.
* @param where A Locale specifying the language of the text being analyzed.
* @return A new instance of BreakIterator that locates sentence boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getSentenceInstance(Locale where)
{
return getBreakInstance(where, KIND_SENTENCE);
}
/**
* Returns a new instance of BreakIterator that locates sentence boundaries.
* This function assumes the text being analyzed is in the default locale's
* language.
* @return A new instance of BreakIterator that locates sentence boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getTitleInstance()
{
return getTitleInstance(Locale.getDefault());
}
/**
* Returns a new instance of BreakIterator that locates sentence boundaries.
* @param where A Locale specifying the language of the text being analyzed.
* @return A new instance of BreakIterator that locates sentence boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getTitleInstance(Locale where)
{
return getBreakInstance(where, KIND_TITLE);
}
/**
* Register a new break iterator of the indicated kind, to use in the given locale.
* Clones of the iterator will be returned
* if a request for a break iterator of the given kind matches or falls back to
* this locale.
* @param iter the BreakIterator instance to adopt.
* @param locale the Locale for which this instance is to be registered
* @param kind the type of iterator for which this instance is to be registered
* @return a registry key that can be used to unregister this instance
* @draft ICU 2.4
*/
public static Object registerInstance(BreakIterator iter, Locale locale, int kind) {
try {
return getService().registerObject(iter, locale, kind);
}
catch (IndexOutOfBoundsException e) {
throw new IllegalArgumentException("unknown kind: " + kind);
}
}
/**
* Unregister a previously-registered BreakIterator using the key returned from the
* register call. Key becomes invalid after this call and should not be used again.
* @param key the registry key returned by a previous call to registerInstance
* @return true if the iterator for the key was successfully unregistered
* @draft ICU 2.4
*/
public static boolean unregister(Object key) {
if (service != null) {
return service.unregisterFactory((Factory)key);
}
return false;
}
private static ICULocaleService service;
private static ICULocaleService getService() {
if (service == null) {
ICULocaleService newService = new ICULocaleService("BreakIterator");
class RBBreakIteratorFactory extends ICUResourceBundleFactory {
protected Object handleCreate(Locale loc, int kind, ICUService service) {
return createBreakInstance(loc, kind);
}
}
newService.registerFactory(new RBBreakIteratorFactory());
synchronized (BreakIterator.class) {
if (service == null) {
service = newService;
}
}
}
return service;
}
private static final String[] KIND_NAMES = {
"Character", "Word", "Line", "Sentence", "Title"
};
private static BreakIterator createBreakInstance(Locale locale, int kind) {
String prefix = KIND_NAMES[kind];
return createBreakInstance(locale,
kind,
prefix + "BreakRules",
prefix + "BreakDictionary");
}
// end of registration
private static BreakIterator getBreakInstance(Locale where, int kind) {
if (iterCache[kind] != null) {
BreakIteratorCache cache = (BreakIteratorCache) iterCache[kind].get();
if (cache != null) {
if (cache.getLocale().equals(where)) {
return cache.createBreakInstance();
}
}
}
BreakIterator result = createBreakInstance(where, kind);
BreakIteratorCache cache = new BreakIteratorCache(where, result);
iterCache[kind] = new SoftReference(cache);
return result;
}
private static BreakIterator createBreakInstance(Locale where,
int kind,
String rulesName,
String dictionaryName) {
// System.out.println("rulesName: "+rulesName);
// System.out.println("dictionaryName: "+dictionaryName);
ResourceBundle bundle = ICULocaleData.getResourceBundle("BreakIteratorRules", where);
String[] classNames = bundle.getStringArray("BreakIteratorClasses");
String rules = bundle.getString(rulesName);
if (classNames[kind].equals("RuleBasedBreakIterator")) {
return new RuleBasedBreakIterator(rules);
}
else if (classNames[kind].equals("DictionaryBasedBreakIterator")) {
try {
// System.out.println(dictionaryName);
Object t = bundle.getObject(dictionaryName);
// System.out.println(t);
URL url = (URL)t;
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[kind] + "\"");
}
/**
* Returns a list of locales for which BreakIterators can be used.
* @return An array of Locales. All of the locales in the array can
* be used when creating a BreakIterator.
*/
public static synchronized Locale[] getAvailableLocales()
{
if (service == null) {
return ICULocaleData.getAvailableLocales();
} else {
return service.getAvailableLocales();
}
}
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();
}
}
}