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.
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Applications that sort through text perform frequent string comparisons. For example, a report generator performs string comparisons when sorting a list of strings in alphabetical order.
If your application audience is limited to people who speak English, you can probably perform string comparisons with the String.compareTo method. The String.compareTo method performs a binary comparison of the Unicode characters within the two strings. For most languages, however, this binary comparison cannot be relied on to sort strings, because the Unicode values do not correspond to the relative order of the characters.
Fortunately the
Collator class allows your application to perform string comparisons for different languages. In this section, you'll learn how to use the Collator class when sorting text.
Collation rules define the sort sequence of strings. These rules vary with locale, because various natural languages sort words differently. Using the predefined collation rules provided by the Collator class, you can sort strings in a locale-independent manner.
In some cases, the predefined collation rules provided by the Collator class may not work for you. For example, you may want to sort strings in a language whose locale is not supported by Collator. In this situation, you can define your own collation rules, and assign them to a RuleBasedCollator object.
With the CollationKey class, you may increase the efficiency of string comparisons. This class converts String objects to sort keys that follow the rules of a given Collator.