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));
}