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Class java.text.BreakIterator

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

public abstract class BreakIterator

extends Object

implements Cloneable, Serializable

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);
      }
 }
 

 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));
     }
 }
 

 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));
     }
 }
 

 public static void printFirst(BreakIterator boundary, String source) {
     int start = boundary.first();
     int end = boundary.next();
     System.out.println(source.substring(start,end));
 }
 

 public static void printLast(BreakIterator boundary, String source) {
     int end = boundary.last();
     int start = boundary.previous();
     System.out.println(source.substring(start,end));
 }
 

 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.

java.text.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(int)

Return the nth boundary from the current boundary

next()

Return the boundary following the current boundary.

previous()

Return the boundary preceding the current boundary.

setText(String)

Set a new text string to be scanned.

setText(CharacterIterator)

Set a new text for scanning.

public static final int DONE

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

protected BreakIterator()

Constructor. BreakIterator is stateless and has no default behavior.

public java.lang.Object clone()

Create a copy of this iterator

Returns:

A copy of this

Overrides:

clone in class Object

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.

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.

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.

public static synchronized java.util.Locale[] getAvailableLocales()

Get the set of Locales for which BreakIterators are installed

Returns:

available locales

public static java.text.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

public static java.text.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

public static java.text.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

public static java.text.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

public static java.text.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

public static java.text.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

public abstract java.text.CharacterIterator getText()

Get the text being scanned

Returns:

the text being scanned

public static java.text.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

public static java.text.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

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.

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.

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).

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.

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.

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.

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