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CollationKey class.
A
CollationKey object represents a sort key for a given String and
Collator. Comparing two CollationKey objects
involves a bitwise comparison of sort keys and is faster than
comparing String objects with the
Collator.compare method. However, generating
CollationKey objects requires time. Therefore if a
String is to be compared just once,
Collator.compare offers better performance.
The example that follows uses a CollationKey object to sort an array of words. Source code for this example is in
KeysDemo.java.
The KeysDemo program creates an array of
CollationKey objects in the main method. To
create a CollationKey, you invoke the
getCollationKey method on a Collator object.
You cannot compare two CollationKey objects unless they
originate from the same Collator. The main
method is as follows:
static public void main(String[] args) {
Collator enUSCollator =
Collator.getInstance (new Locale("en","US"));
String [] words = {
"peach",
"apricot",
"grape",
"lemon"
};
CollationKey[] keys = new CollationKey[words.length];
for (int k = 0; k < keys.length; k ++) {
keys[k] = enUSCollator.getCollationKey(words[k]);
}
sortArray(keys);
printArray(keys);
}
The sortArray method invokes the
CollationKey.compareTo method. The compareTo
method returns an integer less than, equal to, or greater than zero if
the keys[i] object is less than, equal to, or greater than
the keys[j] object. Note that the program compares the
CollationKey objects, not the String objects
from the original array of words. Here is the code for the
sortArray method:
public static void sortArray(CollationKey[] keys) {
CollationKey tmp;
for (int i = 0; i < keys.length; i++) {
for (int j = i + 1; j < keys.length; j++) {
if (keys[i].compareTo(keys[j]) > 0) {
tmp = keys[i];
keys[i] = keys[j];
keys[j] = tmp;
}
}
}
}
The KeysDemo program sorts an array of
CollationKey objects, but the original goal was to sort an
array of String objects. To retrieve the
String representation of each CollationKey,
the program invokes getSourceString in the
displayWords method, as follows:
static void displayWords(CollationKey[] keys) {
for (int i = 0; i < keys.length; i++) {
System.out.println(keys[i].getSourceString());
}
}
The displayWords
method prints the following lines:
apricot grape lemon peach
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