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## org.apache.commons.lang
Class CharSet

    java.lang.Object
      |
      +--org.apache.commons.lang.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.

Since:
  1.0
Version:
  $Id: CharSet.java 471626 2006-11-06 04:02:09Z bayard $
Author:
  Stephen Colebourne, Phil Steitz, Pete Gieser, Gary Gregory
See Also:
  Serialized Form

Field Summary
`static CharSet` | `ASCII_ALPHA` A CharSet defining ASCII alphabetic characters "a-zA-Z".
`static CharSet` | `ASCII_ALPHA_LOWER` A CharSet defining ASCII alphabetic characters "a-z".
`static CharSet` | `ASCII_ALPHA_UPPER` A CharSet defining ASCII alphabetic characters "A-Z".
`static CharSet` | `ASCII_NUMERIC` A CharSet defining ASCII alphabetic characters "0-9".
`protected static Map` | `COMMON` A Map of the common cases used in the factory.
`static CharSet` | `EMPTY` A CharSet defining no characters.

Constructor Summary
`protected` | `CharSet(String setStr)` Constructs a new CharSet using the set syntax.
`protected` | `CharSet(String[] set)` Constructs a new CharSet using the set syntax.

Method Summary
`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.
`CharRange[]` | `getCharRanges()` Gets the internal set as an array of CharRange objects.
`static CharSet` | `getInstance(String setStr)` Factory method to create a new CharSet using a special syntax.
`int` | `hashCode()` Gets a hashCode 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 Detail

### 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 COMMON

  A Map of the common cases used in the factory. Subclasses can add more common patterns if desired.
  Since:
    2.0

Constructor Detail

### CharSet

    protected CharSet(String setStr)

  Constructs a new CharSet using the set syntax.

  Parameters:
    `setStr` - the String describing the set, may be null
  Since:
    2.0

### 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 Detail

### getInstance

    public static CharSet getInstance(String setStr)

  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.

  All CharSet objects returned by this method will be immutable.

  Parameters:
    `setStr` - the String describing the set, may be null
  Returns:
    a CharSet instance
  Since:
    2.0

### add

    protected void add(String str)

  Add a set definition string to the `CharSet`.

  Parameters:
    `str` - set definition string

### getCharRanges

    public CharRange[] getCharRanges()

  Gets the internal set as an array of CharRange objects.

  Returns:
    an array of immutable CharRange objects
  Since:
    2.0

### 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 hashCode compatible with the equals method.

  Overrides:
    `hashCode` in class `Object`
  Returns:
    a suitable hashCode
  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

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