BreakIterator

abstract class BreakIterator : Cloneable

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. The CharacterIterator object must not be modified after having been passed to setText. If the text in the CharacterIterator object is changed, the caller must reset BreakIterator by calling setText.

You use the factory methods provided by this class to create instances of various types of break iterators. In particular, use getWordInstance, getLineInstance, getSentenceInstance, and getCharacterInstance 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. Actual line breaking needs to also consider the available line width and is handled by higher-level software.

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 through character strings, regardless of how the character is stored. The boundaries returned may be those of supplementary characters, combining character sequences, or ligature clusters. 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.

The BreakIterator instances returned by the factory methods of this class are intended for use with natural languages only, not for programming language text. It is however possible to define subclasses that 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));
  }
  

<code>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 &lt; current; p++) {
              if (Character.isLetter(text.codePointAt(p)))
                  return last;
          }
          last = current;
          current = wb.next();
      }
      return BreakIterator.DONE;
  }
  </code>

Summary

Constants

static val DONE: Int

Value: -1

Protected constructors

protected BreakIterator()

Public methods

open fun clone(): Any

abstract fun current(): Int

abstract fun first(): Int

abstract fun following(offset: Int): Int

open static fun getAvailableLocales(): Array<Locale!>!

open static fun getCharacterInstance(): BreakIterator!

open static fun getCharacterInstance(locale: Locale!): BreakIterator!

open static fun getLineInstance(): BreakIterator!

open static fun getLineInstance(locale: Locale!): BreakIterator!

open static fun getSentenceInstance(): BreakIterator!

open static fun getSentenceInstance(locale: Locale!): BreakIterator!

abstract fun getText(): CharacterIterator!

open static fun getWordInstance(): BreakIterator!

open static fun getWordInstance(locale: Locale!): BreakIterator!

open fun isBoundary(offset: Int): Boolean

abstract fun last(): Int

abstract fun next(n: Int): Int

abstract fun next(): Int

open fun preceding(offset: Int): Int

abstract fun previous(): Int

open fun setText(newText: String!): Unit

abstract fun setText(newText: CharacterIterator!): Unit