| Represents a string under the rules of a specific {@code Collator} object.
Comparing two {@code CollationKey} instances returns the relative order of
the strings they represent.
Since the rule set of collators can differ, the sort orders of the same
string under two different {@code Collator} instances might differ. Hence
comparing collation keys generated from different {@code Collator} instances
can give incorrect results.
Both the method {@code CollationKey.compareTo(CollationKey)} and the method
{@code Collator.compare(String, String)} compares two strings and returns
their relative order. The performance characteristics of these two approaches
can differ.
During the construction of a {@code CollationKey}, the entire source string
is examined and processed into a series of bits terminated by a null, that
are stored in the {@code CollationKey}. When
{@code CollationKey.compareTo(CollationKey)} executes, it performs bitwise
comparison on the bit sequences. This can incur startup cost when creating
the {@code CollationKey}, but once the key is created, binary comparisons
are fast. This approach is recommended when the same strings are to be
compared over and over again.
On the other hand, implementations of
{@code Collator.compare(String, String)} can examine and process the strings
only until the first characters differ in order. This approach is
recommended if the strings are to be compared only once.
The following example shows how collation keys can be used to sort a
list of strings:
// 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 way
if( 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());
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