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29. The java.text Package


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The java.text package consists of classes and interfaces that are useful for writing internationalized programs that handle local customs, such as date and time formatting and string alphabetization, correctly. This package is new in Java 1.1. Figure 29.1 shows its class hierarchy.

The NumberFormat class formats numbers, monetary quantities, and percentages as appropriate for the default or specified locale. DateFormat formats dates and times in a locale-specific way. The concrete DecimalFormat and SimpleDateFormat subclasses of these classes can be used for customized number, date, and time formatting. MessageFormat allows substitution of dynamic values, including formatted numbers and dates, into static message strings. ChoiceFormat formats a number using an enumerated set of string values. Collator compares strings according to the customary sorting order for a locale. BreakIterator scans text to find word, line, and sentence boundaries following locale-specfic rules.

Figure 29.1: The java.text package

[Graphic: Figure 29-1]

29.1 java.text.BreakIterator (JDK 1.1)

This class is used to determine character, word, sentence, and line breaks in a block of text in a way that is independent of locale and text-encoding. As an abstract class, BreakIterator cannot be instantiated directly. Instead, you must use one of the class methods getCharacterInstance(), getWordInstance(), getSentenceInstance(), or getLineInstance() to return an instance of a nonabstract subclass of BreakIterator. These various "factory" methods return a BreakIterator object that is configured to locate the requested boundary types, and is localized to work for the optionally specified locale.

Once you have obtained an appropriate BreakIterator object, you use setText() to specify the text that it is to locate boundaries in. To locate boundaries in a Java String object, simply specify the string. To locate boundaries in text that uses some other encoding, you must specify a CharacterIterator object for that text so that the BreakIterator object can locate the individual characters of the text.

Having set the text to be searched, you can determine the character positions of characters, words, sentences, or line breaks with the first(), last(), next(), previous(), current(), and following() methods, which perform the obvious functions. Note that these methods do not return text itself, but merely the position of the appropriate word, sentence, or line break.

public abstract class BreakIterator extends Object implements Cloneable, Serializable {
    // Protected Constructor
            protected BreakIterator();
    // Constants
            public static final int DONE;
    // Class Methods
            public static synchronized Locale[] getAvailableLocales();
            public static BreakIterator getCharacterInstance();
            public static BreakIterator getCharacterInstance(Locale where);
            public static BreakIterator getLineInstance();
            public static BreakIterator getLineInstance(Locale where);
            public static BreakIterator getSentenceInstance();
            public static BreakIterator getSentenceInstance(Locale where);
            public static BreakIterator getWordInstance();
            public static BreakIterator getWordInstance(Locale where);
    // Public Instance Methods
            public Object clone();  // Overrides Object
            public abstract int current();
            public abstract int first();
            public abstract int following(int offset);
            public abstract CharacterIterator getText();
            public abstract int last();
            public abstract int next(int n);
            public abstract int next();
            public abstract int previous();
            public void setText(String newText);
            public abstract void setText(CharacterIterator newText);

Returned By:

BreakIterator.getCharacterInstance(), BreakIterator.getLineInstance(), BreakIterator.getSentenceInstance(), BreakIterator.getWordInstance()

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