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Collation rules define the sort sequence of strings. These rules vary with locale, because various natural languages sort words differently. You can use the predefined collation rules provided by theCollator
class to sort strings in a locale-independent manner.To instantiate the
Collator
class invoke thegetInstance
method. Usually, you create aCollator
for the defaultLocale
, as in the following example:You can also specify a particularCollator myDefaultCollator = Collator.getInstance();Locale
when you create aCollator
, as follows:Collator myFrenchCollator = Collator.getInstance(Locale.FRENCH);The
getInstance
method returns aRuleBasedCollator
, which is a concrete subclass ofCollator
. TheRuleBasedCollator
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 theRuleBasedCollator
, 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. Thecompare
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 toCollator.compare
:
Collator.compare
ExamplesExample 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 calledCollatorDemo
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 anyCollator
. Notice that thesortStrings
method invokes thecompare
method:The Englishpublic 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 sinAccording 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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