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 five built-in types of BreakIterator: *
* 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.charAt(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
* @stable ICU 2.0
*
*/
public abstract class BreakIterator implements Cloneable
{
private static final boolean DEBUG = ICUDebug.enabled("breakiterator");
/**
* 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) {
///CLOVER:OFF
throw new IllegalStateException();
///CLOVER:ON
}
}
/**
* 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 actual iterator being used by the BreakIterator,
* and therefore, this function's return value should be treated as
* const. 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);
/**
* {@icu}
* @stable ICU 2.4
*/
public static final int KIND_CHARACTER = 0;
/**
* {@icu}
* @stable ICU 2.4
*/
public static final int KIND_WORD = 1;
/**
* {@icu}
* @stable ICU 2.4
*/
public static final int KIND_LINE = 2;
/**
* {@icu}
* @stable ICU 2.4
*/
public static final int KIND_SENTENCE = 3;
/**
* {@icu}
* @stable ICU 2.4
*/
public static final int KIND_TITLE = 4;
/**
* @since ICU 2.8
*/
private static final int KIND_COUNT = 5;
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(ULocale.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(ULocale.forLocale(where), KIND_WORD);
}
/**
* {@icu} 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 3.2
*/
public static BreakIterator getWordInstance(ULocale 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(ULocale.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(ULocale.forLocale(where), KIND_LINE);
}
/**
* {@icu} 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 3.2
*/
public static BreakIterator getLineInstance(ULocale 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(ULocale.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(ULocale.forLocale(where), KIND_CHARACTER);
}
/**
* {@icu} 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 3.2
*/
public static BreakIterator getCharacterInstance(ULocale 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(ULocale.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(ULocale.forLocale(where), KIND_SENTENCE);
}
/**
* {@icu} 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 3.2
*/
public static BreakIterator getSentenceInstance(ULocale where)
{
return getBreakInstance(where, KIND_SENTENCE);
}
/**
* {@icu} Returns a new instance of BreakIterator that locates title boundaries.
* This function assumes the text being analyzed is in the default locale's
* language. The iterator returned locates title boundaries as described for
* Unicode 3.2 only. For Unicode 4.0 and above title boundary iteration,
* please use a word boundary iterator. {@link #getWordInstance}
* @return A new instance of BreakIterator that locates title boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getTitleInstance()
{
return getTitleInstance(ULocale.getDefault());
}
/**
* {@icu} Returns a new instance of BreakIterator that locates title boundaries.
* The iterator returned locates title boundaries as described for
* Unicode 3.2 only. For Unicode 4.0 and above title boundary iteration,
* please use Word Boundary iterator.{@link #getWordInstance}
* @param where A Locale specifying the language of the text being analyzed.
* @return A new instance of BreakIterator that locates title boundaries.
* @stable ICU 2.0
*/
public static BreakIterator getTitleInstance(Locale where)
{
return getBreakInstance(ULocale.forLocale(where), KIND_TITLE);
}
/**
* {@icu} Returns a new instance of BreakIterator that locates title boundaries.
* The iterator returned locates title boundaries as described for
* Unicode 3.2 only. For Unicode 4.0 and above title boundary iteration,
* please use Word Boundary iterator.{@link #getWordInstance}
* @param where A Locale specifying the language of the text being analyzed.
* @return A new instance of BreakIterator that locates title boundaries.
* @stable ICU 3.2
s */
public static BreakIterator getTitleInstance(ULocale where)
{
return getBreakInstance(where, KIND_TITLE);
}
/**
* {@icu} Registers 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
* @stable ICU 2.4
*/
public static Object registerInstance(BreakIterator iter, Locale locale, int kind) {
return registerInstance(iter, ULocale.forLocale(locale), kind);
}
/**
* {@icu} Registers 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
* @stable ICU 3.2
*/
public static Object registerInstance(BreakIterator iter, ULocale locale, int kind) {
// If the registered object matches the one in the cache, then
// flush the cached object.
if (iterCache[kind] != null) {
BreakIteratorCache cache = (BreakIteratorCache) iterCache[kind].get();
if (cache != null) {
if (cache.getLocale().equals(locale)) {
iterCache[kind] = null;
}
}
}
return getShim().registerInstance(iter, locale, kind);
}
/**
* {@icu} Unregisters 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
* @stable ICU 2.4
*/
public static boolean unregister(Object key) {
if (key == null) {
throw new IllegalArgumentException("registry key must not be null");
}
// TODO: we don't do code coverage for the following lines
// because in getBreakInstance we always instantiate the shim,
// and test execution is such that we always instantiate a
// breakiterator before we get to the break iterator tests.
// this is for modularization, and we could remove the
// dependencies in getBreakInstance by rewriting part of the
// LocaleData code, or perhaps by accepting it into the
// module.
///CLOVER:OFF
if (shim != null) {
// Unfortunately, we don't know what is being unregistered
// -- what `kind' and what locale -- so we flush all
// caches. This is safe but inefficient if people are
// actively registering and unregistering.
for (int kind=0; kindNote: The actual locale is returned correctly, but the valid * locale is not, in most cases. * @param type type of information requested, either {@link * com.ibm.icu.util.ULocale#VALID_LOCALE} or {@link * com.ibm.icu.util.ULocale#ACTUAL_LOCALE}. * @return the information specified by type, or null if * this object was not constructed from locale data. * @see com.ibm.icu.util.ULocale * @see com.ibm.icu.util.ULocale#VALID_LOCALE * @see com.ibm.icu.util.ULocale#ACTUAL_LOCALE * @draft ICU 2.8 (retain) * @provisional This API might change or be removed in a future release. */ public final ULocale getLocale(ULocale.Type type) { return type == ULocale.ACTUAL_LOCALE ? this.actualLocale : this.validLocale; } /** * Set information about the locales that were used to create this * object. If the object was not constructed from locale data, * both arguments should be set to null. Otherwise, neither * should be null. The actual locale must be at the same level or * less specific than the valid locale. This method is intended * for use by factories or other entities that create objects of * this class. * @param valid the most specific locale containing any resource * data, or null * @param actual the locale containing data used to construct this * object, or null * @see com.ibm.icu.util.ULocale * @see com.ibm.icu.util.ULocale#VALID_LOCALE * @see com.ibm.icu.util.ULocale#ACTUAL_LOCALE */ final void setLocale(ULocale valid, ULocale actual) { // Change the following to an assertion later if ((valid == null) != (actual == null)) { ///CLOVER:OFF throw new IllegalArgumentException(); ///CLOVER:ON } // Another check we could do is that the actual locale is at // the same level or less specific than the valid locale. this.validLocale = valid; this.actualLocale = actual; } /** * The most specific locale containing any resource data, or null. * @see com.ibm.icu.util.ULocale */ private ULocale validLocale; /** * The locale containing data used to construct this object, or * null. * @see com.ibm.icu.util.ULocale */ private ULocale actualLocale; // -------- END ULocale boilerplate -------- }