Class java.text.BreakIterator





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Class java.text.BreakIterator


java.lang.Object
|
+----java.text.BreakIterator



public abstract class BreakIterator
extends Object
implements Cloneable, Serializable

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 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));
}




See Also:
CharacterIterator








DONE
DONE is returned by previous() and next() after all valid
boundaries have been returned.






BreakIterator()
Constructor.






clone()
Create a copy of this iterator


current()
Return character index of the text boundary that was most recently
returned by next(), previous(), first(), or last()


first()
Return the first boundary.

following(int)
Return the first boundary following the specified offset.

getAvailableLocales()
Get the set of Locales for which BreakIterators are installed


getCharacterInstance()
Create BreakIterator for character-breaks using default locale
Returns an instance of a BreakIterator implementing character breaks.

getCharacterInstance(Locale)
Create BreakIterator for character-breaks using specified locale
Returns an instance of a BreakIterator implementing character breaks.

getLineInstance()
Create BreakIterator for line-breaks using default locale.

getLineInstance(Locale)
Create BreakIterator for line-breaks using specfied locale.

getSentenceInstance()
Create BreakIterator for sentence-breaks using default locale
Returns an instance of a BreakIterator implementing sentence breaks.

getSentenceInstance(Locale)
Create BreakIterator for sentence-breaks using specified locale
Returns an instance of a BreakIterator implementing sentence breaks.

getText()
Get the text being scanned


getWordInstance()
Create BreakIterator for word-breaks using default locale.

getWordInstance(Locale)
Create BreakIterator for word-breaks using specified locale.

last()
Return the last boundary.

next()
Return the boundary following the current boundary.

next(int)
Return the nth boundary from the current boundary


previous()
Return the boundary preceding the current boundary.

setText(CharacterIterator)
Set a new text for scanning.

setText(String)
Set a new text string to be scanned.






DONE

public static final int DONE


DONE is returned by previous() and next() after all valid
boundaries have been returned.







BreakIterator

protected BreakIterator()


Constructor. BreakIterator is stateless and has no default behavior.







clone

public Object clone()


Create a copy of this iterator


Returns:
A copy of this
Overrides:
clone in class Object



first

public abstract int first()


Return the first boundary. The iterator's current position is set
to the first boundary.


Returns:
The character index of the first text boundary.



last

public abstract int last()


Return the last boundary. The iterator's current position is set
to the last boundary.


Returns:
The character index of the last text boundary.



next

public abstract int next(int n)


Return the nth boundary from the current boundary


Parameters:
n - which boundary to return. A value of 0
does nothing. Negative values move to previous boundaries
and positive values move to later boundaries.
Returns:
The index of the nth boundary from the current position.



next

public abstract int next()


Return the boundary following the current boundary.


Returns:
The character index of the next text boundary or DONE if all
boundaries have been returned. Equivalent to next(1).



previous

public abstract int previous()


Return the boundary preceding the current boundary.


Returns:
The character index of the previous text boundary or DONE if all
boundaries have been returned.



following

public abstract int following(int offset)


Return the first boundary following the specified offset.
The value returned is always greater than the offset or
the value BreakIterator.DONE


Parameters:
offset - the offset to begin scanning. Valid values
are determined by the CharacterIterator passed to
setText(). Invalid values cause
an IllegalArgumentException to be thrown.
Returns:
The first boundary after the specified offset.



current

public abstract int current()


Return character index of the text boundary that was most recently
returned by next(), previous(), first(), or last()


Returns:
The boundary most recently returned.



getText

public abstract CharacterIterator getText()


Get the text being scanned


Returns:
the text being scanned



setText

public void setText(String newText)


Set a new text string to be scanned. The current scan
position is reset to first().


Parameters:
newText - new text to scan.



setText

public abstract void setText(CharacterIterator newText)


Set a new text for scanning. The current scan
position is reset to first().


Parameters:
newText - new text to scan.



getWordInstance

public static BreakIterator getWordInstance()


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)


Returns:
A BreakIterator for word-breaks
See Also:
getDefault



getWordInstance

public static BreakIterator getWordInstance(Locale where)


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)


Parameters:
where - the local. If a specific WordBreak is not
avaliable for the specified locale, a default WordBreak is returned.
Returns:
A BreakIterator for word-breaks



getLineInstance

public static BreakIterator getLineInstance()


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.


Returns:
A BreakIterator for line-breaks
See Also:
getDefault



getLineInstance

public static BreakIterator getLineInstance(Locale where)


Create BreakIterator for line-breaks using specfied 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.


Parameters:
where - the local. If a specific LineBreak is not
avaliable for the specified locale, a default LineBreak is returned.
Returns:
A BreakIterator for line-breaks



getCharacterInstance

public static BreakIterator getCharacterInstance()


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.


Returns:
A BreakIterator for character-breaks
See Also:
getDefault



getCharacterInstance

public static BreakIterator getCharacterInstance(Locale where)


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.


Parameters:
where - the local. If a specific character break is not
avaliable for the specified local, a default character break is returned.
Returns:
A BreakIterator for character-breaks



getSentenceInstance

public static BreakIterator getSentenceInstance()


Create BreakIterator for sentence-breaks using default locale
Returns an instance of a BreakIterator implementing sentence breaks.


Returns:
A BreakIterator for sentence-breaks
See Also:
getDefault



getSentenceInstance

public static BreakIterator getSentenceInstance(Locale where)


Create BreakIterator for sentence-breaks using specified locale
Returns an instance of a BreakIterator implementing sentence breaks.


Parameters:
where - the local. If a specific SentenceBreak is not
avaliable for the specified local, a default SentenceBreak is returned.
Returns:
A BreakIterator for sentence-breaks



getAvailableLocales

public static synchronized Locale[] getAvailableLocales()


Get the set of Locales for which BreakIterators are installed


Returns:
available locales




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