Class Soundex

src/main/java/org/apache/commons/codec/language/Soundex.java:30–333

Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a general purpose scheme to find word with similar phonemes. This class is thread-safe. Although not strictly immutable, the mutable fields are not actually used.

 * Although not strictly immutable, the mutable fields are not actually used.</p>
 */
public class Soundex implements StringEncoder {

    /**
     * The marker character used to indicate a silent (ignored) character.
     * These are ignored except when they appear as the first character.
     * <p>
     * Note: the {@link #US_ENGLISH_MAPPING_STRING} does not use this mechanism
     * because changing it might break existing code. Mappings that don't contain
     * a silent marker code are treated as though H and W are silent.
     * <p>
     * To override this, use the {@link #Soundex(String, boolean)} constructor.
     * @since 1.11
     */
    public static final char SILENT_MARKER = '-';

    /**
     * This is a default mapping of the 26 letters used in US English. A value of {@code 0} for a letter position
     * means do not encode, but treat as a separator when it occurs between consonants with the same code.
     * <p>
     * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
     * up the value for the constant values page.)
     * <p>
     * <b>Note that letters H and W are treated specially.</b>
     * They are ignored (after the first letter) and don't act as separators
     * between consonants with the same code.
     */
    //                                                      ABCDEFGHIJKLMNOPQRSTUVWXYZ
    public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";

    /**
     * This is a default mapping of the 26 letters used in US English. A value of {@code 0} for a letter position
     * means do not encode.
     *
     * @see Soundex#Soundex(char[])
     */
    private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();

    /**
     * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
     * This treats H and W as silent letters.
     * Apart from when they appear as the first letter, they are ignored.
     * They don't act as separators between duplicate codes.
     *
     * @see #US_ENGLISH_MAPPING_STRING
     */
    public static final Soundex US_ENGLISH = new Soundex();

    /**
     * An instance of Soundex using the Simplified Soundex mapping, as described here:
     * http://west-penwith.org.uk/misc/soundex.htm
     * <p>
     * This treats H and W the same as vowels (AEIOUY).
     * Such letters aren't encoded (after the first), but they do
     * act as separators when dropping duplicate codes.
     * The mapping is otherwise the same as for {@link #US_ENGLISH}
     * <p>
     * @since 1.11
     */