Class BreakIterator

  • All Implemented Interfaces:
    java.lang.AutoCloseable, java.lang.Cloneable

    public class BreakIterator
    extends Managed
    implements java.lang.Cloneable

    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:

    • makeSentenceInstance() returns a BreakIterator that locates boundaries between sentences. This is useful for triple-click selection, for example.
    • makeWordInstance() 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.
    • makeLineInstance() 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.
    • makeCharacterInstance() 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".
    The text boundary positions are found according to the rules described in Unicode Standard Annex #29, Text Boundaries, and Unicode Standard Annex #14, Line Breaking Properties. These are available at http://www.unicode.org/reports/tr14/ and http://www.unicode.org/reports/tr29/.

    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:

    • The beginning and end of the text are always treated as boundary positions.
    • 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).
    • 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().
    • 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.
    • 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.
    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. Note: 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.

    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.makeWordInstance();
              boundary.setText(stringToExamine);
              printEachForward(boundary, stringToExamine);
              //print each sentence in reverse order
              boundary = BreakIterator.makeSentenceInstance(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.makeWordInstance();
         wb.setText(text);
         int wordStart = wb.following(pos);
         for (;;) {
             int wordLimit = wb.next();
             if (wordLimit == BreakIterator.DONE) {
                 return BreakIterator.DONE;
             }
             int wordStatus = wb.getRuleStatus();
             if (wordStatus != BreakIterator.WORD_NONE) {
                 return wordStart;
             }
             wordStart = wordLimit;
          }
     }
     
    The iterator returned by makeWordInstance() 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 getRuleStatus() to identify and ignore boundaries associated with punctuation or other non-word characters.
    • Field Summary

      Fields 
      Modifier and Type Field Description
      U16String _text  
      static int DONE
      DONE is returned by previous() and next() after all valid boundaries have been returned.
      static int WORD_IDEO
      Tag value for words containing ideographic characters, lower limit
      static int WORD_IDEO_LIMIT
      Tag value for words containing ideographic characters, upper limit
      static int WORD_KANA
      Tag value for words containing kana characters, lower limit
      static int WORD_KANA_LIMIT
      Tag value for words containing kana characters, upper limit
      static int WORD_LETTER
      Tag value for words that contain letters, excluding hiragana, katakana or ideographic characters, lower limit.
      static int WORD_LETTER_LIMIT
      Tag value for words containing letters, upper limit
      static int WORD_NONE
      Tag value for "words" that do not fit into any of other categories.
      static int WORD_NONE_LIMIT
      Upper bound for tags for uncategorized words.
      static int WORD_NUMBER
      Tag value for words that appear to be numbers, lower limit.
      static int WORD_NUMBER_LIMIT
      Tag value for words that appear to be numbers, upper limit.
      • Fields inherited from class io.github.humbleui.skija.impl.Native

        _ptr
    • Constructor Summary

      Constructors 
      Constructor Description
      BreakIterator​(long ptr)  
    • Field Detail

      • DONE

        public static final int DONE
        DONE is returned by previous() and next() after all valid boundaries have been returned.
        See Also:
        Constant Field Values
      • WORD_NONE

        public static final int WORD_NONE
        Tag value for "words" that do not fit into any of other categories. Includes spaces and most punctuation.
        See Also:
        Constant Field Values
      • WORD_NONE_LIMIT

        public static final int WORD_NONE_LIMIT
        Upper bound for tags for uncategorized words.
        See Also:
        Constant Field Values
      • WORD_NUMBER

        public static final int WORD_NUMBER
        Tag value for words that appear to be numbers, lower limit.
        See Also:
        Constant Field Values
      • WORD_NUMBER_LIMIT

        public static final int WORD_NUMBER_LIMIT
        Tag value for words that appear to be numbers, upper limit.
        See Also:
        Constant Field Values
      • WORD_LETTER

        public static final int WORD_LETTER
        Tag value for words that contain letters, excluding hiragana, katakana or ideographic characters, lower limit.
        See Also:
        Constant Field Values
      • WORD_LETTER_LIMIT

        public static final int WORD_LETTER_LIMIT
        Tag value for words containing letters, upper limit
        See Also:
        Constant Field Values
      • WORD_KANA

        public static final int WORD_KANA
        Tag value for words containing kana characters, lower limit
        See Also:
        Constant Field Values
      • WORD_KANA_LIMIT

        public static final int WORD_KANA_LIMIT
        Tag value for words containing kana characters, upper limit
        See Also:
        Constant Field Values
      • WORD_IDEO

        public static final int WORD_IDEO
        Tag value for words containing ideographic characters, lower limit
        See Also:
        Constant Field Values
      • WORD_IDEO_LIMIT

        public static final int WORD_IDEO_LIMIT
        Tag value for words containing ideographic characters, upper limit
        See Also:
        Constant Field Values
    • Constructor Detail

      • BreakIterator

        @Internal
        public BreakIterator​(long ptr)
    • Method Detail

      • close

        public void close()
        Specified by:
        close in interface java.lang.AutoCloseable
        Overrides:
        close in class Managed
      • clone

        public BreakIterator clone()
        Create a copy of this iterator
        Overrides:
        clone in class java.lang.Object
      • makeCharacterInstance

        public static BreakIterator makeCharacterInstance()
        Returns a new BreakIterator instance for character breaks for the default locale.
      • makeCharacterInstance

        public static BreakIterator makeCharacterInstance​(java.lang.String locale)
        Returns a new BreakIterator instance for character breaks for the given locale.
      • makeWordInstance

        public static BreakIterator makeWordInstance()
        Returns a new BreakIterator instance for word breaks for the default locale.
      • makeWordInstance

        public static BreakIterator makeWordInstance​(java.lang.String locale)
        Returns a new BreakIterator instance for word breaks for the given locale.
      • makeLineInstance

        public static BreakIterator makeLineInstance()
        Returns a new BreakIterator instance for line breaks for the default locale.
      • makeLineInstance

        public static BreakIterator makeLineInstance​(java.lang.String locale)
        Returns a new BreakIterator instance for line breaks for the given locale.
      • makeSentenceInstance

        public static BreakIterator makeSentenceInstance()
        Returns a new BreakIterator instance for sentence breaks for the default locale.
      • makeSentenceInstance

        public static BreakIterator makeSentenceInstance​(java.lang.String locale)
        Returns a new BreakIterator instance for sentence breaks for the given locale.
      • current

        public int current()
        Returns character index of the text boundary that was most recently returned by next(), next(int), previous(), first(), last(), following(int) or preceding(int). If any of these methods returns DONE because either first or last text boundary has been reached, it returns the first or last text boundary depending on which one is reached.
      • next

        public int next()
        Returns the boundary following the current boundary. If the current boundary is the last text boundary, it returns DONE and the iterator's current position is unchanged. Otherwise, the iterator's current position is set to the boundary following the current boundary.
      • next

        public int next​(int n)
        Advances the iterator either forward or backward the specified number of steps. Negative values move backward, and positive values move forward. This is equivalent to repeatedly calling next() or previous().
        Parameters:
        n - The number of steps to move. The sign indicates the direction (negative is backwards, and positive is forwards).
        Returns:
        The character offset of the boundary position n boundaries away from the current one.
      • previous

        public int previous()
        Returns the boundary following the current boundary. If the current boundary is the last text boundary, it returns DONE and the iterator's current position is unchanged. Otherwise, the iterator's current position is set to the boundary following the current boundary.
      • first

        public int first()
        Returns the first boundary. The iterator's current position is set to the first text boundary.
      • last

        public int last()
        Returns the last boundary. The iterator's current position is set to the last text boundary.
      • preceding

        public int preceding​(int offset)
        Returns the last boundary preceding the specified character offset. If the specified offset is equal to the first text boundary, it returns DONE and the iterator's current position is unchanged. Otherwise, the iterator's current position is set to the returned boundary. The value returned is always less than the offset or the value DONE.
      • following

        public int following​(int offset)
        Returns the first boundary following the specified character offset. If the specified offset is equal to the last text boundary, it returns DONE and the iterator's current position is unchanged. Otherwise, the iterator's current position is set to the returned boundary. The value returned is always greater than the offset or the value DONE.
      • isBoundary

        public boolean isBoundary​(int offset)
        Returns true if the specified character offset is a text boundary.
      • getRuleStatus

        public int getRuleStatus()

        For rule-based BreakIterators, return the status tag from the break rule that determined the boundary at the current iteration position.

        For break iterator types that do not support a rule status, a default value of 0 is returned.

        Returns:
        The status from the break rule that determined the boundary at the current iteration position.
      • getRuleStatuses

        public int[] getRuleStatuses()
        For RuleBasedBreakIterators, get the status (tag) values from the break rule(s) that determined the the boundary at the current iteration position.

        For break iterator types that do not support rule status, no values are returned.

        Returns:
        an array with the status values.
      • setText

        public void setText​(java.lang.String text)
        Set a new text string to be scanned. The current scan position is reset to first().
      • _nGetFinalizer

        @Internal
        public static long _nGetFinalizer()
      • _nMake

        @Internal
        public static long _nMake​(int type,
                                  java.lang.String locale)
      • _nClone

        @Internal
        public static long _nClone​(long ptr)
      • _nCurrent

        @Internal
        public static int _nCurrent​(long ptr)
      • _nNext

        @Internal
        public static int _nNext​(long ptr)
      • _nPrevious

        @Internal
        public static int _nPrevious​(long ptr)
      • _nFirst

        @Internal
        public static int _nFirst​(long ptr)
      • _nLast

        @Internal
        public static int _nLast​(long ptr)
      • _nPreceding

        @Internal
        public static int _nPreceding​(long ptr,
                                      int offset)
      • _nFollowing

        @Internal
        public static int _nFollowing​(long ptr,
                                      int offset)
      • _nIsBoundary

        @Internal
        public static boolean _nIsBoundary​(long ptr,
                                           int offset)
      • _nGetRuleStatus

        @Internal
        public static int _nGetRuleStatus​(long ptr)
      • _nGetRuleStatuses

        @Internal
        public static int[] _nGetRuleStatuses​(long ptr)
      • _nSetText

        @Internal
        public static void _nSetText​(long ptr,
                                     long textPtr)