java.text
Class CollationKey

java.lang.Object
  java.text.CollationKey

All Implemented Interfaces:

Comparable < CollationKey >

public abstract final 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 , RuleBasedCollator

Constructor Summary
protected	CollationKey ( String           CollationKey constructor.

 

Method Summary
abstract  int	compareTo ( CollationKey           Compare this CollationKey to the target CollationKey.
boolean	equals ( Object           Compare this CollationKey and the target CollationKey for equality.
String	getSourceString ()           Returns the String that this CollationKey represents.
abstract  byte[]  int	toByteArray hashCode ()           Converts the CollationKey to           Creates a sequence of bits. hash code for this CollationKey.
byte[]	toByteArray ()           Converts the CollationKey to a sequence of bits.

 

Methods inherited from class java.lang. Object
clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait

 

Constructor Method Detail

CollationKey compareTo

protected 
public int CollationKey compareTo ( StringCollationKey source)  target) 

CollationKey constructor. 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.

Specified by:

compareTo in interface Comparable < CollationKey >

Parameters:

source - - the source string. target - target CollationKey

Throws: Returns:

NullPointerException - if source is null. 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.

Since: See Also:

1.6 Collator.compare(java.lang.String, java.lang.String)

Method Detail

compareTo equals

public abstract int 
public boolean compareTo equals ( CollationKeyObject target)

Compare this CollationKey to and the target CollationKey. 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.

Specified by: Overrides:

compareTo equals in interface Comparable in class Object < CollationKey >

Parameters:

target - target the CollationKey to compare to.

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. Returns true if two objects are equal, false otherwise.

See Also:

Collator.compare(java.lang.String, java.lang.String) Object.hashCode() , Hashtable

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.

Overrides:

hashCode in class Object

Returns:

the hash value based on the string's collation order.

See Also:

Object.equals(java.lang.Object) , Hashtable

getSourceString

public String getSourceString()

Returns the String that this CollationKey represents.

toByteArray

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.