Spec-Zone .ru
спецификации, руководства, описания, API
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JavaTM 2 Platform Std. Ed. v1.3.1 |
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java.lang.Object | +--java.text.BreakIterator
The 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 BreakIterator
s 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
Print each element in orderpublic 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 reverse orderpublic 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 first elementpublic 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 last elementpublic static void printFirst(BreakIterator boundary, String source) { int start = boundary.first(); int end = boundary.next(); System.out.println(source.substring(start,end)); }
Print the element at a specified positionpublic static void printLast(BreakIterator boundary, String source) { int end = boundary.last(); int start = boundary.previous(); System.out.println(source.substring(start,end)); }
Find the next wordpublic 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)); }
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.)
CharacterIterator
Field Summary | |
static int |
DONE
DONE is returned by previous() and next() after all valid boundaries have been returned. |
Constructor Summary | |
protected |
BreakIterator()
Constructor. |
Method Summary | |
Object |
clone()
Create a copy of this iterator |
abstract int |
current()
Return character index of the text boundary that was most recently returned by next(), previous(), first(), or last() |
abstract int |
first()
Return the first boundary. |
abstract int |
following(int offset)
Return the first boundary following the specified offset. |
static Locale[] |
getAvailableLocales()
Get the set of Locales for which BreakIterators are installed |
static BreakIterator |
getCharacterInstance()
Create BreakIterator for character-breaks using default locale Returns an instance of a BreakIterator implementing character breaks. |
static BreakIterator |
getCharacterInstance(Locale where)
Create BreakIterator for character-breaks using specified locale Returns an instance of a BreakIterator implementing character breaks. |
static BreakIterator |
getLineInstance()
Create BreakIterator for line-breaks using default locale. |
static BreakIterator |
getLineInstance(Locale where)
Create BreakIterator for line-breaks using specified locale. |
static BreakIterator |
getSentenceInstance()
Create BreakIterator for sentence-breaks using default locale Returns an instance of a BreakIterator implementing sentence breaks. |
static BreakIterator |
getSentenceInstance(Locale where)
Create BreakIterator for sentence-breaks using specified locale Returns an instance of a BreakIterator implementing sentence breaks. |
abstract CharacterIterator |
getText()
Get the text being scanned |
static BreakIterator |
getWordInstance()
Create BreakIterator for word-breaks using default locale. |
static BreakIterator |
getWordInstance(Locale where)
Create BreakIterator for word-breaks using specified locale. |
boolean |
isBoundary(int offset)
Return true if the specified position is a boundary position. |
abstract int |
last()
Return the last boundary. |
abstract int |
next()
Return the boundary following the current boundary. |
abstract int |
next(int n)
Return the nth boundary from the current boundary |
int |
preceding(int offset)
Return the last boundary preceding the specfied offset. |
abstract int |
previous()
Return the boundary preceding the current boundary. |
abstract void |
setText(CharacterIterator newText)
Set a new text for scanning. |
void |
setText(String newText)
Set a new text string to be scanned. |
Methods inherited from class java.lang.Object |
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
public static final int DONE
Constructor Detail |
protected BreakIterator()
Method Detail |
public Object clone()
clone
in class Object
public abstract int first()
public abstract int last()
public abstract int next(int n)
n
- which boundary to return. A value of 0
does nothing. Negative values move to previous boundaries
and positive values move to later boundaries.public abstract int next()
public abstract int previous()
public abstract int following(int offset)
offset
- the offset to begin scanning. Valid values
are determined by the CharacterIterator passed to
setText(). Invalid values cause
an IllegalArgumentException to be thrown.public int preceding(int offset)
offset
- the offset to begin scanning. Valid values are
determined by the CharacterIterator passed to setText().
Invalid values cause an IllegalArgumentException to be thrown.public boolean isBoundary(int offset)
offset
- the offset to check.public abstract int current()
public abstract CharacterIterator getText()
public void setText(String newText)
newText
- new text to scan.public abstract void setText(CharacterIterator newText)
newText
- new text to scan.public static BreakIterator getWordInstance()
Locale.getDefault()
public static BreakIterator getWordInstance(Locale where)
where
- the local. If a specific WordBreak is not
avaliable for the specified locale, a default WordBreak is returned.public static BreakIterator getLineInstance()
Locale.getDefault()
public static BreakIterator getLineInstance(Locale where)
where
- the local. If a specific LineBreak is not
avaliable for the specified locale, a default LineBreak is returned.public static BreakIterator getCharacterInstance()
Locale.getDefault()
public static BreakIterator getCharacterInstance(Locale where)
where
- the local. If a specific character break is not
avaliable for the specified local, a default character break is returned.public static BreakIterator getSentenceInstance()
Locale.getDefault()
public static BreakIterator getSentenceInstance(Locale where)
where
- the local. If a specific SentenceBreak is not
avaliable for the specified local, a default SentenceBreak is returned.public static Locale[] getAvailableLocales()
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JavaTM 2 Platform Std. Ed. v1.3.1 |
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