ACollationKey represents aString under the rules of a specificCollator object. Comparing twoCollationKeys returns the relative order of theStrings they represent. UsingCollationKeys to compareStrings is generally faster than usingCollator.compare. Thus, when theStrings must be compared multiple times, for example when sorting a list ofStrings. It's more efficient to useCollationKeys.

You can not createCollationKeys directly. Rather, generate them by callingCollator.getCollationKey. You can only compareCollationKeys generated from the sameCollator object.

Generating aCollationKey for aString involves examining the entireString and converting it to series of bits that can be compared bitwise. This allows fast comparisons once the keys are generated. The cost of generating keys is recouped in faster comparisons whenStrings need to be compared many times. On the other hand, the result of a comparison is often determined by the first couple of characters of eachString.Collator.compare examines only as many characters as it needs which allows it to be faster when doing single comparisons.

The following example shows howCollationKeys might be used to sort a list ofStrings.

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// Create an array of CollationKeys for the Strings to be sorted.Collator myCollator = Collator.getInstance();CollationKey[] keys = new CollationKey[3];keys[0] = myCollator.getCollationKey("Tom");keys[1] = myCollator.getCollationKey("Dick");keys[2] = myCollator.getCollationKey("Harry");sort(keys);//...// Inside body of sort routine, compare keys this wayif (keys[i].compareTo(keys[j]) > 0)   // swap keys[i] and keys[j]//...// Finally, when we've returned from sort.System.out.println(keys[0].getSourceString());System.out.println(keys[1].getSourceString());System.out.println(keys[2].getSourceString());