java.text.Collator

java.text.Collator

public class java.text.Collator extends java.lang.Object implements java.util.Comparator, java.lang.Cloneable
since: ???
direct subclasses: java.text.RuleBasedCollator
see also: java.text.RuleBasedCollator, java.text.CollationKey, java.text.CollationElementIterator, java.util.Locale
fields: CANONICAL_DECOMPOSITION, FULL_DECOMPOSITION, IDENTICAL, NO_DECOMPOSITION, PRIMARY, SECONDARY, TERTIARY
constructors: Collator()
methods: clone(), compare(Object o1, Object o2), compare(String source, String target), equals(Object that), equals(String source, String target), getAvailableLocales(), getCollationKey(String source), getDecomposition(), getInstance(), getInstance(Locale desiredLocale), getStrength(), hashCode(), setDecomposition(int decompositionMode), setStrength(int newStrength)

The Collator class performs locale-sensitive String comparison. You use this class to build searching and sorting routines for natural language text.

Collator is an abstract base class. Subclasses implement specific collation strategies. One subclass, RuleBasedCollator, is currently provided with the Java 2 platform and is applicable to a wide set of languages. Other subclasses may be created to handle more specialized needs.

Like other locale-sensitive classes, you can use the static factory method, getInstance, to obtain the appropriate Collator object for a given locale. You will only need to look at the subclasses of Collator if you need to understand the details of a particular collation strategy or if you need to modify that strategy.

The following example shows how to compare two strings using the Collator for the default locale.

// Compare two strings in the default locale
Collator myCollator = Collator.getInstance();
if( myCollator.compare("abc", "ABC") < 0 )
System.out.println("abc is less than ABC");
else
System.out.println("abc is greater than or equal to ABC");

You can set a Collator's strength property to determine the level of difference considered significant in comparisons. Four strengths are provided: PRIMARY, SECONDARY, TERTIARY, and IDENTICAL. The exact assignment of strengths to language features is locale dependant. For example, in Czech, "e" and "f" are considered primary differences, while "e" and "ê" are secondary differences, "e" and "E" are tertiary differences and "e" and "e" are identical. The following shows how both case and accents could be ignored for US English.

//Get the Collator for US English and set its strength to PRIMARY
Collator usCollator = Collator.getInstance(Locale.US);
usCollator.setStrength(Collator.PRIMARY);
if( usCollator.compare("abc", "ABC") == 0 ) {
System.out.println("Strings are equivalent");
}

For comparing Strings exactly once, the compare method provides the best performance. When sorting a list of Strings however, it is generally necessary to compare each String multiple times. In this case, CollationKeys provide better performance. The CollationKey class converts a String to a series of bits that can be compared bitwise against other CollationKeys. A CollationKey is created by a Collator object for a given String.
Note: CollationKeys from different Collators can not be compared. See the class description for CollationKey for an example using CollationKeys.

source: Sun's Java documentation for JDK 1.3
Sun Microsystems: www.sun.com   |   Sun's Java: java.sun.com   |   JDK 1.3 API docs: http://java.sun.com/j2se/1.3/docs/api/index.html