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Java in a Nutshell

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The java.text Package

29.3 java.text.ChoiceFormat (JDK 1.1)

This class is a subclass of Format that converts a number to a String in a way that is reminiscent of a switch statement or an enumerated type. Each ChoiceFormat object has an array of doubles known as its "limits" and an array of strings known as its "formats." When the format() method is called to format a number x, the ChoiceFormat finds an index i such that:

limits[i] <= x < limits[i+1]

If x is less than the first element of the array, the first element is used, and if it is greater than the last, the last element is used. Once the index i has been determined, it is used as the index into the array of strings, and the indexed string is returned as the result of the format() method.

A ChoiceFormat object may also be created by encoding its "limits" and "formats" into a single string known as its "pattern." A typical pattern looks like the one that follows, used to return the singular or plural form of a word, based on the numeric value passed to the format() method:

ChoiceFormat cf = new ChoiceFormat("0#errors|1#error|2#errors");

A ChoiceFormat object created in this way returns the string "errors" when it formats the number 0, or any number greater than or equal to 2. It returns "error" when it formats the number 1. In the syntax shown here, note the pound sign (#) used to separate the limit number from the string that corresponds to that case and the vertical bar (|) used to separate the individual cases. You can use the applyPattern() method to change the pattern used by a ChoiceFormat object; use toPattern() to query the pattern it uses.

public class ChoiceFormat extends NumberFormat {
    // Public Constructors
            public ChoiceFormat(String newPattern);
            public ChoiceFormat(double[] limits, String[] formats);
    // Class Methods
            public static final double nextDouble(double d);
            public static double nextDouble(double d, boolean positive);
            public static final double previousDouble(double d);
    // Public Instance Methods
            public void applyPattern(String newPattern);
            public Object clone();  // Overrides NumberFormat
            public boolean equals(Object obj);  // Overrides NumberFormat
            public StringBuffer format(long number, StringBuffer toAppendTo,
            FieldPosition status);  // Defines NumberFormat
            public StringBuffer format(double number, StringBuffer toAppendTo,
            FieldPosition status);  // Defines NumberFormat
            public Object[] getFormats();
            public double[] getLimits();
            public int hashCode();  // Overrides NumberFormat
            public Number parse(String text, ParsePosition status);  // Defines NumberFormat
            public void setChoices(double[] limits, String[] formats);
            public String toPattern();


Object->Format(Serializable, Cloneable)->NumberFormat(Cloneable)->ChoiceFormat

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