UnicodeSet

Class Overview

A mutable set of Unicode characters and multicharacter strings. Objects of this class represent character classes used in regular expressions. A character specifies a subset of Unicode code points. Legal code points are U+0000 to U+10FFFF, inclusive.

The UnicodeSet class is not designed to be subclassed.

UnicodeSet supports two APIs. The first is the operand API that allows the caller to modify the value of a UnicodeSet object. It conforms to Java 2's java.util.Set interface, although UnicodeSet does not actually implement that interface. All methods of Set are supported, with the modification that they take a character range or single character instead of an Object, and they take a UnicodeSet instead of a Collection. The operand API may be thought of in terms of boolean logic: a boolean OR is implemented by add, a boolean AND is implemented by retain, a boolean XOR is implemented by complement taking an argument, and a boolean NOT is implemented by complement with no argument. In terms of traditional set theory function names, add is a union, retain is an intersection, remove is an asymmetric difference, and complement with no argument is a set complement with respect to the superset range MIN_VALUE-MAX_VALUE

The second API is the applyPattern()/toPattern() API from the java.text.Format-derived classes. Unlike the methods that add characters, add categories, and control the logic of the set, the method applyPattern() sets all attributes of a UnicodeSet at once, based on a string pattern.

Pattern syntax

Patterns are accepted by the constructors and the applyPattern() methods and returned by the toPattern() method. These patterns follow a syntax similar to that employed by version 8 regular expression character classes. Here are some simple examples:

[]	No characters
[a]	The character 'a'
[ae]	The characters 'a' and 'e'
[a-e]	The characters 'a' through 'e' inclusive, in Unicode code point order
[\\u4E01]	The character U+4E01
[a{ab}{ac}]	The character 'a' and the multicharacter strings "ab" and "ac"
[\p{Lu}]	All characters in the general category Uppercase Letter

Any character may be preceded by a backslash in order to remove any special meaning. White space characters, as defined by UCharacterProperty.isRuleWhiteSpace(), are ignored, unless they are escaped.

Property patterns specify a set of characters having a certain property as defined by the Unicode standard. Both the POSIX-like "[:Lu:]" and the Perl-like syntax "\p{Lu}" are recognized. For a complete list of supported property patterns, see the User's Guide for UnicodeSet at http://oss.software.ibm.com/icu/userguide/unicodeSet.html. Actual determination of property data is defined by the underlying Unicode database as implemented by UCharacter.

Patterns specify individual characters, ranges of characters, and Unicode property sets. When elements are concatenated, they specify their union. To complement a set, place a '^' immediately after the opening '['. Property patterns are inverted by modifying their delimiters; "[:^foo]" and "\P{foo}". In any other location, '^' has no special meaning.

Ranges are indicated by placing two a '-' between two characters, as in "a-z". This specifies the range of all characters from the left to the right, in Unicode order. If the left character is greater than or equal to the right character it is a syntax error. If a '-' occurs as the first character after the opening '[' or '[^', or if it occurs as the last character before the closing ']', then it is taken as a literal. Thus "[a\\-b]", "[-ab]", and "[ab-]" all indicate the same set of three characters, 'a', 'b', and '-'.

Sets may be intersected using the '&' operator or the asymmetric set difference may be taken using the '-' operator, for example, "[[:L:]&[\\u0000-\\u0FFF]]" indicates the set of all Unicode letters with values less than 4096. Operators ('&' and '|') have equal precedence and bind left-to-right. Thus "[[:L:]-[a-z]-[\\u0100-\\u01FF]]" is equivalent to "[[[:L:]-[a-z]]-[\\u0100-\\u01FF]]". This only really matters for difference; intersection is commutative.

[a]	The set containing 'a'
[a-z]	The set containing 'a' through 'z' and all letters in between, in Unicode order
[^a-z]	The set containing all characters but 'a' through 'z', that is, U+0000 through 'a'-1 and 'z'+1 through U+10FFFF
[[pat1][pat2]]	The union of sets specified by pat1 and pat2
[[pat1]&[pat2]]	The intersection of sets specified by pat1 and pat2
[[pat1]-[pat2]]	The asymmetric difference of sets specified by pat1 and pat2
[:Lu:] or \p{Lu}	The set of characters having the specified Unicode property; in this case, Unicode uppercase letters
[:^Lu:] or \P{Lu}	The set of characters not having the given Unicode property

Warning: you cannot add an empty string ("") to a UnicodeSet.

Formal syntax

pattern :=	('[' '^'? item* ']') | property
item :=	char | (char '-' char) | pattern-expr
pattern-expr :=	pattern | pattern-expr pattern | pattern-expr op pattern
op :=	'&' | '-'
special :=	'[' | ']' | '-'
char :=	any character that is not special | ('\\' any character) | ('\u' hex hex hex hex)
hex :=	any character for which Character.digit(c, 16) returns a non-negative result
property :=	a Unicode property set pattern

Legend: a := b   a may be replaced by b a? zero or one instance of a a* one or more instances of a a | b either a or b 'a' the literal string between the quotes

Summary

Constants
int	IGNORE_SPACE	Bitmask for constructor and applyPattern() indicating that white space should be ignored.
int	MAX_VALUE	Maximum value that can be stored in a UnicodeSet.
int	MIN_VALUE	Minimum value that can be stored in a UnicodeSet.

[Expand] Inherited Constants
From interface sun.text.normalizer.UnicodeMatcher char ETHER The character at index i, where i < contextStart || i >= contextLimit, is ETHER.

Public Constructors
	UnicodeSet() Constructs an empty set.
	UnicodeSet(int start, int end) Constructs a set containing the given range.
	UnicodeSet(String pattern) Constructs a set from the given pattern.

Public Methods
StringBuffer	_generatePattern(StringBuffer result, boolean escapeUnprintable) Generate and append a string representation of this set to result.
UnicodeSet	add(int start, int end) Adds the specified range to this set if it is not already present.
final UnicodeSet	add(int c) Adds the specified character to this set if it is not already present.
final UnicodeSet	add(String s) Adds the specified multicharacter to this set if it is not already present.
UnicodeSet	addAll(UnicodeSet c) Adds all of the elements in the specified set to this set if they're not already present.
final UnicodeSet	applyPattern(String pattern) Modifies this set to represent the set specified by the given pattern.
UnicodeSet	applyPropertyAlias(String propertyAlias, String valueAlias, SymbolTable symbols) This method is deprecated. This is a draft API and might change in a future release of ICU.
UnicodeSet	clear() Removes all of the elements from this set.
UnicodeSet	complement(int start, int end) Complements the specified range in this set.
UnicodeSet	complement() This is equivalent to complement(MIN_VALUE, MAX_VALUE).
boolean	contains(int c) Returns true if this set contains the given character.
int	getRangeCount() Iteration method that returns the number of ranges contained in this set.
int	getRangeEnd(int index) Iteration method that returns the last character in the specified range of this set.
int	getRangeStart(int index) Iteration method that returns the first character in the specified range of this set.
UnicodeSet	removeAll(UnicodeSet c) Removes from this set all of its elements that are contained in the specified set.
UnicodeSet	retainAll(UnicodeSet c) Retains only the elements in this set that are contained in the specified set.
UnicodeSet	set(UnicodeSet other) Make this object represent the same set as other.

[Expand] Inherited Methods

From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait() Causes the current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object. final void wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed. final void wait(long timeout) Causes the current thread to wait until either another thread invokes the notify() method or the notifyAll() method for this object, or a specified amount of time has elapsed.