Package org.apache.commons.lang3

Class CharSet

java.lang.Object

org.apache.commons.lang3.CharSet

All Implemented Interfaces:

Serializable

public class CharSet
extends Object
implements Serializable

A set of characters.

Instances are immutable, but instances of subclasses may not be.

#ThreadSafe#

Since:

1.0

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final CharSet	ASCII_ALPHA	A CharSet defining ASCII alphabetic characters "a-zA-Z".
static final CharSet	ASCII_ALPHA_LOWER	A CharSet defining ASCII alphabetic characters "a-z".
static final CharSet	ASCII_ALPHA_UPPER	A CharSet defining ASCII alphabetic characters "A-Z".
static final CharSet	ASCII_NUMERIC	A CharSet defining ASCII alphabetic characters "0-9".
protected static final Map<String,CharSet>	COMMON	A Map of the common cases used in the factory.
static final CharSet	EMPTY	A CharSet defining no characters.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	CharSet(String... set)	Constructs a new CharSet using the set syntax.

Method Summary

Modifier and Type	Method	Description
protected void	add(String str)	Add a set definition string to the CharSet.
boolean	contains(char ch)	Does the CharSet contain the specified character ch.
boolean	equals(Object obj)	Compares two CharSet objects, returning true if they represent exactly the same set of characters defined in the same way.
static CharSet	getInstance(String... setStrs)	Factory method to create a new CharSet using a special syntax.
int	hashCode()	Gets a hash code compatible with the equals method.
String	toString()	Gets a string representation of the set.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

EMPTY

public static final CharSet EMPTY

A CharSet defining no characters.

Since:

2.0

ASCII_ALPHA

public static final CharSet ASCII_ALPHA

A CharSet defining ASCII alphabetic characters "a-zA-Z".

Since:

2.0

ASCII_ALPHA_LOWER

public static final CharSet ASCII_ALPHA_LOWER

A CharSet defining ASCII alphabetic characters "a-z".

Since:

2.0

ASCII_ALPHA_UPPER

public static final CharSet ASCII_ALPHA_UPPER

A CharSet defining ASCII alphabetic characters "A-Z".

Since:

2.0

ASCII_NUMERIC

public static final CharSet ASCII_NUMERIC

A CharSet defining ASCII alphabetic characters "0-9".

Since:

2.0

COMMON

protected static final Map<String,CharSet> COMMON

A Map of the common cases used in the factory. Subclasses can add more common patterns if desired

Since:

2.0

Constructor Details

CharSet

protected CharSet(String... set)

Constructs a new CharSet using the set syntax. Each string is merged in with the set.

Parameters:

set - Strings to merge into the initial set

Throws:

NullPointerException - if set is null

Method Details

getInstance

public static CharSet getInstance(String... setStrs)

Factory method to create a new CharSet using a special syntax.

• null or empty string ("") - set containing no characters
• Single character, such as "a" - set containing just that character
• Multi character, such as "a-e" - set containing characters from one character to the other
• Negated, such as "^a" or "^a-e" - set containing all characters except those defined
• Combinations, such as "abe-g" - set containing all the characters from the individual sets

The matching order is:

1. Negated multi character range, such as "^a-e"
2. Ordinary multi character range, such as "a-e"
3. Negated single character, such as "^a"
4. Ordinary single character, such as "a"

Matching works left to right. Once a match is found the search starts again from the next character.

If the same range is defined twice using the same syntax, only one range will be kept. Thus, "a-ca-c" creates only one range of "a-c".

If the start and end of a range are in the wrong order, they are reversed. Thus "a-e" is the same as "e-a". As a result, "a-ee-a" would create only one range, as the "a-e" and "e-a" are the same.

The set of characters represented is the union of the specified ranges.

There are two ways to add a literal negation character (^):

• As the last character in a string, e.g. CharSet.getInstance("a-z^")
• As a separate element, e.g. CharSet.getInstance("^", "a-z")

Examples using the negation character:

     CharSet.getInstance("^a-c").contains('a') = false
     CharSet.getInstance("^a-c").contains('d') = true
     CharSet.getInstance("^^a-c").contains('a') = true // (only '^' is negated)
     CharSet.getInstance("^^a-c").contains('^') = false
     CharSet.getInstance("^a-cd-f").contains('d') = true
     CharSet.getInstance("a-c^").contains('^') = true
     CharSet.getInstance("^", "a-c").contains('^') = true
 

All CharSet objects returned by this method will be immutable.

Parameters:

setStrs - Strings to merge into the set, may be null

Returns:

a CharSet instance

Since:

2.4

add

protected void add(String str)

Add a set definition string to the CharSet.

Parameters:

str - set definition string

contains

public boolean contains(char ch)

Does the CharSet contain the specified character ch.

Parameters:

ch - the character to check for

Returns:

true if the set contains the characters

equals

public boolean equals(Object obj)

Compares two CharSet objects, returning true if they represent exactly the same set of characters defined in the same way.

The two sets abc and a-c are not equal according to this method.

Overrides:

equals in class Object

Parameters:

obj - the object to compare to

Returns:

true if equal

Since:

2.0

hashCode

public int hashCode()

Gets a hash code compatible with the equals method.

Overrides:

hashCode in class Object

Returns:

a suitable hash code

Since:

2.0

toString

public String toString()

Gets a string representation of the set.

Overrides:

toString in class Object

Returns:

string representation of the set