Class InternetDomainName

guava/src/com/google/common/net/InternetDomainName.java:73–643

An immutable well-formed internet domain name, such as {@code com} or {@code foo.co.uk}. Only syntactic analysis is performed; no DNS lookups or other network interactions take place. Thus there is no guarantee that the domain actually exists on the internet. <p>One common use of this class is to d

 * @since 5.0
 */
@GwtCompatible
@Immutable
public final class InternetDomainName {

  private static final CharMatcher DOTS_MATCHER = CharMatcher.anyOf(".\u3002\uFF0E\uFF61");
  private static final Splitter DOT_SPLITTER = Splitter.on('.');

  /**
   * Value of {@link #publicSuffixIndex()} or {@link #registrySuffixIndex()} which indicates that no
   * relevant suffix was found.
   */
  private static final int NO_SUFFIX_FOUND = -1;

  /**
   * Value of {@link #publicSuffixIndexCache} or {@link #registrySuffixIndexCache} which indicates
   * that they were not initialized yet.
   */
  private static final int SUFFIX_NOT_INITIALIZED = -2;

  /**
   * Maximum parts (labels) in a domain name. This value arises from the 255-octet limit described
   * in <a href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11 with the fact that the
   * encoding of each part occupies at least two bytes (dot plus label externally, length byte plus
   * label internally). Thus, if all labels have the minimum size of one byte, 127 of them will fit.
   */
  private static final int MAX_PARTS = 127;

  /**
   * Maximum length of a full domain name, including separators, and leaving room for the root
   * label. See <a href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11.
   */
  private static final int MAX_LENGTH = 253;

  /**
   * Maximum size of a single part of a domain name. See <a
   * href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11.
   */
  private static final int MAX_DOMAIN_PART_LENGTH = 63;

  /** The full domain name, converted to lower case. */
  private final String name;

  /** The parts of the domain name, converted to lower case. */
  private final ImmutableList<String> parts;

  /**
   * Cached value of #publicSuffixIndex(). Do not use directly.
   *
   * <p>Since this field isn't {@code volatile}, if an instance of this class is shared across
   * threads before it is initialized, then each thread is likely to compute their own copy of the
   * value.
   */
  @SuppressWarnings("Immutable")
  @LazyInit
  private int publicSuffixIndexCache = SUFFIX_NOT_INITIALIZED;

  /**
   * Cached value of #registrySuffixIndex(). Do not use directly.