The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
The BreakIterator
class is locale-sensitive, because text boundaries vary with language. For example, the syntax rules for line breaks are not the same for all languages. To determine which locales the BreakIterator
class supports, invoke the getAvailableLocales
method, as follows:
Locale[] locales = BreakIterator.getAvailableLocales();
You can analyze four kinds of boundaries with the BreakIterator
class: character, word, sentence, and potential line break. When instantiating a BreakIterator
, you invoke the appropriate factory method:
getCharacterInstance
getWordInstance
getSentenceInstance
getLineInstance
Each instance of BreakIterator
can detect just one type of boundary. If you want to locate both character and word boundaries, for example, you create two separate instances.
A BreakIterator
has an imaginary cursor that points to the current boundary in a string of text. You can move this cursor within the text with the previous
and the next
methods. For example, if you've created a BreakIterator
with getWordInstance
, the cursor moves to the next word boundary in the text every time you invoke the next
method. The cursor-movement methods return an integer indicating the position of the boundary. This position is the index of the character in the text string that would follow the boundary. Like string indexes, the boundaries are zero-based. The first boundary is at 0, and the last boundary is the length of the string. The following figure shows the word boundaries detected by the next
and previous
methods in a line of text:
You should use the BreakIterator
class only with natural-language text. To tokenize a programming language, use the StreamTokenizer
class.
The sections that follow give examples for each type of boundary analysis. The coding examples are from the source code file named
BreakIteratorDemo.java
.