Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class CollationKey - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档
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java.text
Class CollationKey
java.lang.Object | +--java.text.CollationKey
- public final class CollationKey
- extends Object
- implements Comparable
- extends Object
A CollationKey represents a String under the
rules of a specific Collator object. Comparing two
CollationKeys returns the relative order of the
Strings they represent. Using CollationKeys
to compare Strings is generally faster than using
Collator.compare. Thus, when the Strings
must be compared multiple times, for example when sorting a list
of Strings. It's more efficient to use CollationKeys.
You can not create CollationKeys directly. Rather,
generate them by calling Collator.getCollationKey.
You can only compare CollationKeys generated from
the same Collator object.
Generating a CollationKey for a String
involves examining the entire String
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 when Strings 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 each String.
Collator.compare examines only as many characters as it needs which
allows it to be faster when doing single comparisons.
The following example shows how CollationKeys might 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() );
- See Also:
Collator,RuleBasedCollator
| Method Summary | |
int |
compareTo(CollationKey target)
Compare this CollationKey to the target CollationKey. |
int |
compareTo(Object o)
Compares this CollationKey with the specified Object for order. |
boolean |
equals(Object target)
Compare this CollationKey and the target CollationKey for equality. |
String |
getSourceString()
Returns the String that this CollationKey represents. |
int |
hashCode()
Creates a hash code for this CollationKey. |
byte[] |
toByteArray()
Converts the CollationKey to a sequence of bits. |
| Methods inherited from class java.lang.Object |
clone,
finalize,
getClass,
notify,
notifyAll,
toString,
wait,
wait,
wait |
| Method Detail |
compareTo
public int compareTo(CollationKey target)
- Compare this CollationKey to the target CollationKey. The collation rules of the
Collator object which created these keys are applied. Note:
CollationKeys created by different Collators can not be compared.
- Parameters:
target- target CollationKey- Returns:
- Returns an integer value. Value is less than zero if this is less than target, value is zero if this and target are equal and value is greater than zero if this is greater than target.
- See Also:
Collator.compare(java.lang.String, java.lang.String)
compareTo
public int compareTo(Object o)
- Compares this CollationKey with the specified Object for order. Returns
a negative integer, zero, or a positive integer as this CollationKey
is less than, equal to, or greater than the given Object.
- Specified by:
- compareTo in interface Comparable
- Parameters:
o- the Object to be compared.- Returns:
- a negative integer, zero, or a positive integer as this Collation Key is less than, equal to, or greater than the given Object.
- Throws:
- ClassCastException - the specified Object is not a CollationKey.
- Since:
- JDK1.2
- See Also:
Comparable
equals
public boolean equals(Object target)
- Compare this CollationKey and the target CollationKey for equality.
The collation rules of the Collator object which created these keys are applied.
Note: CollationKeys created by different Collators can not be
compared.
- Parameters:
target- the CollationKey to compare to.- Returns:
- Returns true if two objects are equal, false otherwise.
hashCode
public int hashCode()
- Creates a hash code for this CollationKey. The hash value is calculated on the
key itself, not the String from which the key was created. Thus
if x and y are CollationKeys, then x.hashCode(x) == y.hashCode() if
x.equals(y) is true. This allows language-sensitive comparison in a hash table.
See the CollatinKey class description for an example.
- Returns:
- the hash value based on the string's collation order.
getSourceString
public String getSourceString()
- Returns the String that this CollationKey represents.
toByteArray
public byte[] toByteArray()
- Converts the CollationKey to a sequence of bits. If two CollationKeys
could be legitimately compared, then one could compare the byte arrays
for each of those keys to obtain the same result. Byte arrays are
organized most significant byte first.
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