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public abstract class Collator extends Object implements Comparator, Cloneable
The Collator
class performs locale-sensitive
String
comparison. You use this class to build
searching and sorting routines for natural language text.
Collator
is an abstract base class. Subclasses
implement specific collation strategies. One subclass,
RuleBasedCollator
, is currently provided with
the Java Platform and is applicable to a wide set of languages. Other
subclasses may be created to handle more specialized needs.
Like other locale-sensitive classes, you can use the static
factory method, getInstance
, to obtain the appropriate
Collator
object for a given locale. You will only need
to look at the subclasses of Collator
if you need
to understand the details of a particular collation strategy or
if you need to modify that strategy.
The following example shows how to compare two strings using
the Collator
for the default locale.
// Compare two strings in the default locale Collator myCollator = Collator.getInstance(); if( myCollator.compare("abc", "ABC") < 0 ) System.out.println("abc is less than ABC"); else System.out.println("abc is greater than or equal to ABC");
You can set a Collator
's strength property
to determine the level of difference considered significant in
comparisons. Four strengths are provided: PRIMARY
,
SECONDARY
, TERTIARY
, and IDENTICAL
.
The exact assignment of strengths to language features is
locale dependant. For example, in Czech, "e" and "f" are considered
primary differences, while "e" and "ě" are secondary differences,
"e" and "E" are tertiary differences and "e" and "e" are identical.
The following shows how both case and accents could be ignored for
US English.
//Get the Collator for US English and set its strength to PRIMARY Collator usCollator = Collator.getInstance(Locale.US); usCollator.setStrength(Collator.PRIMARY); if( usCollator.compare("abc", "ABC") == 0 ) { System.out.println("Strings are equivalent"); }
For comparing String
s exactly once, the compare
method provides the best performance. When sorting a list of
String
s however, it is generally necessary to compare each
String
multiple times. In this case, CollationKey
s
provide better performance. The CollationKey
class converts
a String
to a series of bits that can be compared bitwise
against other CollationKey
s. A CollationKey
is
created by a Collator
object for a given String
.
Note: CollationKey
s from different
Collator
s can not be compared. See the class description
for {@link CollationKey}
for an example using CollationKey
s.
Field Summary | |
---|---|
static int |
CANONICAL_DECOMPOSITION
Decomposition mode value. |
static int |
FULL_DECOMPOSITION
Decomposition mode value. |
static int |
IDENTICAL
Collator strength value. |
static int |
NO_DECOMPOSITION
Decomposition mode value. |
static int |
PRIMARY
Collator strength value. |
static int |
SECONDARY
Collator strength value. |
static int |
TERTIARY
Collator strength value. |
Constructor Summary | |
---|---|
protected |
Collator() Default constructor. |
Method Summary | |
---|---|
Object |
clone() Overrides Cloneable |
int |
Compares its two arguments for order. |
abstract int |
Compares the source string to the target string according to the collation rules for this Collator. |
boolean |
Compares the equality of two Collators. |
boolean |
Convenience method for comparing the equality of two strings based on this Collator's collation rules. |
static Locale[] |
Returns an array of all locales for which the getInstance methods of this class can return
localized instances.
|
abstract CollationKey |
getCollationKey(String source) Transforms the String into a series of bits that can be compared bitwise to other CollationKeys. |
int |
Get the decomposition mode of this Collator. |
static Collator |
Gets the Collator for the current default locale. |
static Collator |
getInstance(Locale desiredLocale) Gets the Collator for the desired locale. |
int |
Returns this Collator's strength property. |
abstract int |
hashCode() Generates the hash code for this Collator. |
void |
setDecomposition(int decompositionMode) Set the decomposition mode of this Collator. |
void |
setStrength(int newStrength) Sets this Collator's strength property. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
public static final int CANONICAL_DECOMPOSITION
CANONICAL_DECOMPOSITION corresponds to Normalization Form D as described in Unicode Technical Report #15.
public static final int FULL_DECOMPOSITION
FULL_DECOMPOSITION corresponds to Normalization Form KD as described in Unicode Technical Report #15.
public static final int IDENTICAL
public static final int NO_DECOMPOSITION
public static final int PRIMARY
public static final int SECONDARY
public static final int TERTIARY
Constructor Detail |
---|
protected Collator()
Method Detail |
---|
public Object clone()
clone
in class Object
public int compare(Object o1, Object o2)
This implementation merely returns
compare((String)o1, (String)o2)
.
o1
o2
public abstract int compare(String source, String target)
For a one time comparison, this method has the best performance. If a given String will be involved in multiple comparisons, CollationKey.compareTo has the best performance. See the Collator class description for an example using CollationKeys.
source
- the source string.target
- the target string.public boolean equals(Object that)
equals
in class Object
that
- the Collator to be compared with this.public boolean equals(String source, String target)
source
- the source string to be compared with.target
- the target string to be compared with.public static synchronized Locale[] getAvailableLocales()
getInstance
methods of this class can return
localized instances.
The returned array represents the union of locales supported
by the Java runtime and by installed
{@link java.text.spi.CollatorProvider CollatorProvider} implementations.
It must contain at least a Locale instance equal to
{@link java.util.Locale#US Locale.US}.
Collator
instances are available.public abstract CollationKey getCollationKey(String source)
source
- the string to be transformed into a collation key.public synchronized int getDecomposition()
The three values for decomposition mode are:
public static synchronized Collator getInstance()
public static synchronized Collator getInstance(Locale desiredLocale)
desiredLocale
- the desired locale.public synchronized int getStrength()
public abstract int hashCode()
hashCode
in class Object
public synchronized void setDecomposition(int decompositionMode)
decompositionMode
- the new decomposition mode.public synchronized void setStrength(int newStrength)
newStrength
- the new strength value.
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