# Class AlphabetConverter

java.lang.Object
org.apache.commons.text.AlphabetConverter

public final class AlphabetConverter extends Object

Convert from one alphabet to another, with the possibility of leaving certain characters unencoded.

The target and 'do not encode' languages must be in the Unicode BMP, but the source language does not.

The encoding will all be of a fixed length, except for the 'do not encode' chars, which will be of length 1

## Sample usage

    Character[] originals;   // a, b, c, d
    Character[] encoding;    // 0, 1, d
    Character[] doNotEncode; // d

    AlphabetConverter ac = AlphabetConverter.createConverterFromChars(originals,
    encoding, doNotEncode);

    ac.encode("a");    // 00
    ac.encode("b");    // 01
    ac.encode("c");    // 0d
    ac.encode("d");    // d
    ac.encode("abcd"); // 00010dd

#ThreadSafe# AlphabetConverter class methods are thread-safe as they do not change internal state.

Since:
  1.0

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static AlphabetConverter`
  `createConverter(Integer[] original, Integer[] encoding, Integer[] doNotEncode)`
  Creates an alphabet converter, for converting from the original alphabet, to the encoded alphabet, while leaving the characters in doNotEncode as they are (if possible).
  `static AlphabetConverter`
  `createConverterFromChars(Character[] original, Character[] encoding, Character[] doNotEncode)`
  Creates an alphabet converter, for converting from the original alphabet, to the encoded alphabet, while leaving the characters in doNotEncode as they are (if possible).
  `static AlphabetConverter`
  `createConverterFromMap(Map<Integer,String> originalToEncoded)`
  Creates a new converter from a map.
  `String`
  `decode(String encoded)`
  Decodes a given string.
  `String`
  `encode(String original)`
  Encodes a given string.
  `boolean`
  `equals(Object obj)`
  `int`
  `getEncodedCharLength()`
  Gets the length of characters in the encoded alphabet that are necessary for each character in the original alphabet.
  `Map<Integer,String>`
  `getOriginalToEncoded()`
  Gets the mapping from integer code point of source language to encoded string.
  `int`
  `hashCode()`
  `String`
  `toString()`

  ### Methods inherited from class Object

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

- ## Method Details

  - ### createConverter

    public static AlphabetConverter createConverter(Integer[] original, Integer[] encoding, Integer[] doNotEncode)
    Creates an alphabet converter, for converting from the original alphabet, to the encoded alphabet, while leaving the characters in doNotEncode as they are (if possible).

    Duplicate letters in either original or encoding will be ignored.

    Parameters:
      `original` - an array of ints representing the original alphabet in code points.
      `encoding` - an array of ints representing the alphabet to be used for encoding, in code points.
      `doNotEncode` - an array of ints representing the chars to be encoded using the original alphabet - every char here must appear in both the previous params.
    Returns:
      The AlphabetConverter.
    Throws:
      `IllegalArgumentException` - if an AlphabetConverter cannot be constructed.

  - ### createConverterFromChars

    public static AlphabetConverter createConverterFromChars(Character[] original, Character[] encoding, Character[] doNotEncode)
    Creates an alphabet converter, for converting from the original alphabet, to the encoded alphabet, while leaving the characters in doNotEncode as they are (if possible).

    Duplicate letters in either original or encoding will be ignored.

    Parameters:
      `original` - an array of chars representing the original alphabet
      `encoding` - an array of chars representing the alphabet to be used for encoding
      `doNotEncode` - an array of chars to be encoded using the original alphabet - every char here must appear in both the previous params
    Returns:
      The AlphabetConverter
    Throws:
      `IllegalArgumentException` - if an AlphabetConverter cannot be constructed

  - ### createConverterFromMap

    public static AlphabetConverter createConverterFromMap(Map<Integer,String> originalToEncoded)
    Creates a new converter from a map.
    Parameters:
      `originalToEncoded` - a map returned from getOriginalToEncoded().
    Returns:
      The reconstructed AlphabetConverter.
    See Also:
      - `getOriginalToEncoded()`

  - ### decode

    public String decode(String encoded) throws UnsupportedEncodingException
    Decodes a given string.
    Parameters:
      `encoded` - a string that has been encoded using this AlphabetConverter.
    Returns:
      The decoded string, `null` if the given string is null.
    Throws:
      `UnsupportedEncodingException` - if unexpected characters that cannot be handled are encountered.

  - ### encode

    public String encode(String original) throws UnsupportedEncodingException
    Encodes a given string.
    Parameters:
      `original` - the string to be encoded.
    Returns:
      The encoded string, `null` if the given string is null.
    Throws:
      `UnsupportedEncodingException` - if chars that are not supported are encountered.

  - ### equals

    public boolean equals(Object obj)
    Overrides:
      `equals` in class `Object`

  - ### getEncodedCharLength

    public int getEncodedCharLength()
    Gets the length of characters in the encoded alphabet that are necessary for each character in the original alphabet.
    Returns:
      The length of the encoded char.

  - ### getOriginalToEncoded

    public Map<Integer,String> getOriginalToEncoded()
    Gets the mapping from integer code point of source language to encoded string. Use to reconstruct converter from serialized map.
    Returns:
      The original map.

  - ### hashCode

    public int hashCode()
    Overrides:
      `hashCode` in class `Object`

  - ### toString

    public String toString()
    Overrides:
      `toString` in class `Object`