CollationKey

public abstract class CollationKey extends Object
implements Comparable<CollationKey>

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
• ERROR(/RuleBasedCollator)

Protected Constructor Summary

CollationKey(String source) CollationKey constructor.

Public Method Summary

abstract int	compareTo(CollationKey target) Compare this CollationKey to the target CollationKey.
String	getSourceString() Returns the String that this CollationKey represents.
abstract byte[]	toByteArray() Converts the CollationKey to a sequence of bits.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.lang.Comparable

abstract int

compareTo(CollationKey o) Compares this object with the specified object for order.

Protected Constructors

protected CollationKey (String source)

CollationKey constructor.

Parameters

source	the source string

Throws

NullPointerException	if source is null

Public Methods

public abstract 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

• Comparator.compare(T, T)

public String getSourceString ()

Returns the String that this CollationKey represents.

Returns

• the source string of this CollationKey

public abstract 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.

Returns

• a byte array representation of the CollationKey