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Collator class to sort strings in a locale-independent
manner.
To instantiate the Collator class invoke the
getInstance method. Usually, you create a
Collator for the default Locale, as in the
following example:
Collator myDefaultCollator = Collator.getInstance();
Locale when you create a
Collator, as follows:
Collator myFrenchCollator = Collator.getInstance(Locale.FRENCH);
The getInstance method returns a
RuleBasedCollator, which is a concrete subclass of
Collator. The RuleBasedCollator contains a
set of rules that determine the sort order of strings for the locale
you specify. These rules are predefined for each locale. Because the
rules are encapsulated within the RuleBasedCollator, your
program won't need special routines to deal with the way collation
rules vary with language.
You invoke the Collator.compare method to perform a
locale-independent string comparison. The compare method
returns an integer less than, equal to, or greater than zero when the
first string argument is less than, equal to, or greater than the
second string argument. The following table contains some sample calls
to Collator.compare:
| Example | Return Value | Explanation |
|---|---|---|
myCollator.compare("abc", "def") |
-1 |
"abc" is less than "def" |
myCollator.compare("rtf", "rtf") |
0 |
the two strings are equal |
myCollator.compare("xyz", "abc") |
1 |
"xyz" is greater than "abc" |
You use the compare method when performing sort operations.
The sample program called
CollatorDemo
uses the compare method to sort an array of English and
French words. This program shows what can happen when you sort the same
list of words with two different collators:
Collator fr_FRCollator = Collator.getInstance(new Locale("fr","FR"));
Collator en_USCollator = Collator.getInstance(new Locale("en","US"));
The method for sorting, called sortStrings, can be used
with any Collator. Notice that the
sortStrings method invokes the compare
method:
public static void sortStrings(Collator collator,
String[] words) {
String tmp;
for (int i = 0; i < words.length; i++) {
for (int j = i + 1; j < words.length; j++) {
if (collator.compare(words[i], words[j]) > 0) {
tmp = words[i];
words[i] = words[j];
words[j] = tmp;
}
}
}
}
Collator sorts the words as follows:
peach péché pêche sin
According to the collation rules of the French language, the preceding
list is in the wrong order. In French péché should follow
pêche in a sorted list. The French Collator sorts
the array of words correctly, as follows:
peach pêche péché sin
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