Class ColognePhonetic

All Implemented Interfaces:
Encoder, StringEncoder

public class ColognePhonetic extends Object implements StringEncoder
Encodes a string into a Cologne Phonetic value.

Implements the Kölner Phonetik (Cologne Phonetic) algorithm issued by Hans Joachim Postel in 1969.

The Kölner Phonetik is a phonetic algorithm which is optimized for the German language. It is related to the well-known soundex algorithm.


  • Step 1:

    After preprocessing (conversion to upper case, transcription of germanic umlauts, removal of non alphabetical characters) the letters of the supplied text are replaced by their phonetic code according to the following table.
    (Source: Wikipedia (de): Kölner Phonetik -- Buchstabencodes)
    Letter Context Code
    A, E, I, J, O, U, Y 0
    H -
    B 1
    P not before H
    D, T not before C, S, Z 2
    F, V, W 3
    P before H
    G, K, Q 4
    C at onset before A, H, K, L, O, Q, R, U, X
    before A, H, K, O, Q, U, X except after S, Z
    X not after C, K, Q 48
    L 5
    M, N 6
    R 7
    S, Z 8
    C after S, Z
    at onset except before A, H, K, L, O, Q, R, U, X
    not before A, H, K, O, Q, U, X
    D, T before C, S, Z
    X after C, K, Q


    "Müller-Lüdenscheidt" => "MULLERLUDENSCHEIDT" => "6005507500206880022"
  • Step 2:

    Collapse of all multiple consecutive code digits.


    "6005507500206880022" => "6050750206802"
  • Step 3:

    Removal of all codes "0" except at the beginning. This means that two or more identical consecutive digits can occur if they occur after removing the "0" digits.


    "6050750206802" => "65752682"

This class is thread-safe.

See Also:
  • Constructor Details

  • Method Details

    • colognePhonetic

      public String colognePhonetic(String text)

      Implements the Kölner Phonetik algorithm.

      In contrast to the initial description of the algorithm, this implementation does the encoding in one pass.

      text - The source text to encode
      the corresponding encoding according to the Kölner Phonetik algorithm
    • encode

      public Object encode(Object object) throws EncoderException
      Description copied from interface: Encoder
      Encodes an "Object" and returns the encoded content as an Object. The Objects here may just be byte[] or Strings depending on the implementation used.
      Specified by:
      encode in interface Encoder
      object - An object to encode
      An "encoded" Object
      EncoderException - An encoder exception is thrown if the encoder experiences a failure condition during the encoding process.
    • encode

      public String encode(String text)
      Description copied from interface: StringEncoder
      Encodes a String and returns a String.
      Specified by:
      encode in interface StringEncoder
      text - the String to encode
      the encoded String
    • isEncodeEqual

      public boolean isEncodeEqual(String text1, String text2)
      Compares the first encoded string to the second encoded string.
      text1 - source text to encode before testing for equality.
      text2 - source text to encode before testing for equality.
      true if the encoding the first string equals the encoding of the second string, false otherwise