Added in API level 1

CollationKey

abstract class CollationKey : Comparable<CollationKey!>
kotlin.Any
   ↳ java.text.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.

<code>// 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]) &gt; 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());
  </code>

Summary

Protected constructors
CollationKey(source: String!)

CollationKey constructor.

Public methods
abstract Int

Compare this CollationKey to the target CollationKey.

open String!

Returns the String that this CollationKey represents.

abstract ByteArray!

Converts the CollationKey to a sequence of bits.

Protected constructors

CollationKey

Added in API level 9
protected CollationKey(source: String!)

CollationKey constructor.

Parameters
source String!: the source string
Exceptions
java.lang.NullPointerException if source is null

Public methods

compareTo

Added in API level 1
abstract fun compareTo(other: CollationKey!): Int

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
o the object to be compared.
target target CollationKey
Return
Int 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.
Exceptions
java.lang.NullPointerException if the specified object is null
java.lang.ClassCastException if the specified object's type prevents it from being compared to this object.

See Also

    getSourceString

    Added in API level 1
    open fun getSourceString(): String!

    Returns the String that this CollationKey represents.

    Return
    String! the source string of this CollationKey

    toByteArray

    Added in API level 1
    abstract fun toByteArray(): ByteArray!

    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.

    Return
    ByteArray! a byte array representation of the CollationKey