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JavaTM 2 Platform Std. Ed. v1.3 |
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java.lang.Object | +--java.text.Collator
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 2 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 "ê" 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 Strings exactly once, the compare
method provides the best performance. When sorting a list of
Strings however, it is generally necessary to compare each
String multiple times. In this case, CollationKeys
provide better performance. The CollationKey class converts
a String to a series of bits that can be compared bitwise
against other CollationKeys. A CollationKey is
created by a Collator object for a given String.
Note: CollationKeys from different
Collators can not be compared. See the class description
for CollationKey
for an example using CollationKeys.
RuleBasedCollator,
CollationKey,
CollationElementIterator,
Locale| 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 |
compare(Object o1,
Object o2)
Compares its two arguments for order. |
abstract int |
compare(String source,
String target)
Compares the source string to the target string according to the collation rules for this Collator. |
boolean |
equals(Object that)
Compares the equality of two Collators. |
boolean |
equals(String source,
String target)
Convenience method for comparing the equality of two strings based on this Collator's collation rules. |
static Locale[] |
getAvailableLocales()
Get the set of Locales for which Collators are installed. |
abstract CollationKey |
getCollationKey(String source)
Transforms the String into a series of bits that can be compared bitwise to other CollationKeys. |
int |
getDecomposition()
Get the decomposition mode of this Collator. |
static Collator |
getInstance()
Gets the Collator for the current default locale. |
static Collator |
getInstance(Locale desiredLocale)
Gets the Collator for the desired locale. |
int |
getStrength()
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 |
finalize, getClass, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
public static final int PRIMARY
setStrength(int),
getStrength()public static final int SECONDARY
setStrength(int),
getStrength()public static final int TERTIARY
setStrength(int),
getStrength()public static final int IDENTICAL
public static final int NO_DECOMPOSITION
getDecomposition(),
setDecomposition(int)public static final int CANONICAL_DECOMPOSITION
CANONICAL_DECOMPOSITION corresponds to Normalization Form D as described in Unicode Technical Report #15.
getDecomposition(),
setDecomposition(int)public static final int FULL_DECOMPOSITION
FULL_DECOMPOSITION corresponds to Normalization Form DC as described in Unicode Technical Report #15.
getDecomposition(),
setDecomposition(int)| Constructor Detail |
protected Collator()
getInstance()| Method Detail |
public static Collator getInstance()
Locale.getDefault()public static Collator getInstance(Locale desiredLocale)
desiredLocale - the desired locale.Locale,
ResourceBundle
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.CollationKey,
getCollationKey(java.lang.String)
public int compare(Object o1,
Object o2)
This implementation merely returns
compare((String)o1, (String)o2) .
compare in interface ComparatorClassCastException - the arguments cannot be cast to Strings.Comparatorpublic abstract CollationKey getCollationKey(String source)
source - the string to be transformed into a collation key.CollationKey,
compare(java.lang.String, java.lang.String)
public boolean equals(String source,
String target)
source - the source string to be compared with.target - the target string to be compared with.compare(java.lang.String, java.lang.String)public int getStrength()
setStrength(int),
PRIMARY,
SECONDARY,
TERTIARY,
IDENTICALpublic void setStrength(int newStrength)
the - new strength value.IllegalArgumentException - If the new strength value is not one of
PRIMARY, SECONDARY, TERTIARY or IDENTICAL.getStrength(),
PRIMARY,
SECONDARY,
TERTIARY,
IDENTICALpublic int getDecomposition()
The three values for decomposition mode are:
setDecomposition(int),
NO_DECOMPOSITION,
CANONICAL_DECOMPOSITION,
FULL_DECOMPOSITIONpublic void setDecomposition(int decompositionMode)
the - new decomposition modeIllegalArgumentException - If the given value is not a valid decomposition
mode.getDecomposition(),
NO_DECOMPOSITION,
CANONICAL_DECOMPOSITION,
FULL_DECOMPOSITIONpublic static Locale[] getAvailableLocales()
public Object clone()
clone in class Objectjava.lang.ObjectCloneNotSupportedException - if the object's class does not
support the Cloneable interface. Subclasses
that override the clone method can also
throw this exception to indicate that an instance cannot
be cloned.OutOfMemoryError - if there is not enough memory.Cloneablepublic boolean equals(Object that)
equals in interface Comparatorequals in class Objectthat - the Collator to be compared with this.public abstract int hashCode()
hashCode in class Objectjava.lang.ObjectObject.equals(java.lang.Object),
Hashtable
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JavaTM 2 Platform Std. Ed. v1.3 |
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