java.lang.Object | |
↳ | java.text.CollationKey |
Represents a string under the rules of a specific Collator
object.
Comparing two 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 Collator
instances might differ. Hence
comparing collation keys generated from different Collator
instances
can give incorrect results.
Both the method CollationKey.compareTo(CollationKey)
and the method
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 CollationKey
, the entire source string
is examined and processed into a series of bits terminated by a null, that
are stored in the CollationKey
. When
CollationKey.compareTo(CollationKey)
executes, it performs bitwise
comparison on the bit sequences. This can incur startup cost when creating
the 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
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());
Protected Constructors | |||||||||||
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Public Methods | |||||||||||
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Compares this collation key to the given collation key.
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Returns the string from which this collation key was created.
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Returns this collation key as a byte array.
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Inherited Methods | |||||||||||
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From class
java.lang.Object
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From interface
java.lang.Comparable
|
Compares this collation key to the given collation key.
value | the other collation key. |
---|
value
,
0 if they are equal, and a positive value if this key is greater.
Returns the string from which this collation key was created.
Returns this collation key as a byte array.