*
   * @param string a string reference to check
   * @return {@code true} if the string is null or is the empty string
   */
  public static boolean isNullOrEmpty(@CheckForNull String string) {
    return Platform.stringIsNullOrEmpty(string);
  }

  /**
   * Returns a string, of length at least {@code minLength}, consisting of {@code string} prepended

        ImmutableMap.<String, Integer>builder().put("abc", 1).put("def", 2).put("ghi", 3).build();
    String toTest =
        MoreObjects.toStringHelper(new TestClass())
            .add("field1", "This is string.")
            .add("field2", Arrays.asList("abc", "def", "ghi"))
            .add("field3", map)
            .toString();
    final String expected =
        "TestClass{"

  }

  // A simple type whose .toString() will return the same value each time, but without maintaining
  // a strong reference to that value.
  static class Key {
    private final int value;
    private WeakReference<String> toString;

    Key(int value) {
      this.value = value;
    }

    @Override
    public synchronized String toString() {
      String s;
      if (toString != null) {

    String knownOutput = "8cbf764cbe2e4623d99a41354adfd390";

    Mac mac = Mac.getInstance("HmacMD5");
    mac.init(SHA1_KEY);
    assertEquals(knownOutput, HashCode.fromBytes(mac.doFinal()).toString());
    assertEquals(knownOutput, Hashing.hmacMd5(SHA1_KEY).newHasher().hash().toString());
  }

  public void testKnownInputs() throws Exception {
    String knownOutput = "9753980fe94daa8ecaa82216519393a9";

  private final String toString;

  MessageDigestHashFunction(String algorithmName, String toString) {
    this.prototype = getMessageDigest(algorithmName);
    this.bytes = prototype.getDigestLength();
    this.toString = checkNotNull(toString);
    this.supportsClone = supportsClone(prototype);
  }

  MessageDigestHashFunction(String algorithmName, int bytes, String toString) {

      return arithmetic.add(a, b);
    }

    @Override
    public String toString() {
      return arithmetic.toString();
    }
  }

  private interface ParameterTypesDifferent {
    void foo(
        String s,
        Runnable r,
        Number n,
        Iterable<?> it,
        boolean b,
        Equivalence<String> eq,
        Exception e,
        InputStream in,
        Comparable<?> c,

   *
   * @since 11.0
   */
  public final String join(Iterator<? extends @Nullable Object> parts) {
    return appendTo(new StringBuilder(), parts).toString();
  }

  /**
   * Returns a string containing the string representation of each of {@code parts}, using the
   * previously configured separator between each.
   */
  public final String join(@Nullable Object[] parts) {

  @Param({"0", "1", "16", "32", "100"})
  int componentLength;

  private Iterable<String> components;

  @BeforeExperiment
  void setUp() {
    String component = Strings.repeat("a", componentLength);
    String[] raw = new String[count];
    Arrays.fill(raw, component);
    components = Arrays.asList(raw);
  }

  /** {@link Joiner} with a string delimiter. */
  @Benchmark
  int joinerWithStringDelimiter(int reps) {

  /** The Greek letter delta, used in unicode testing. */
  private static final String DELTA = "\u0394";

  /** A domain part which is valid under lenient validation, but invalid under strict validation. */
  static final String LOTS_OF_DELTAS = Strings.repeat(DELTA, 62);

  private static final String ALMOST_TOO_MANY_LEVELS = Strings.repeat("a.", 127);

  private static final String ALMOST_TOO_LONG = Strings.repeat("aaaaa.", 40) + "1234567890.c";

    return new Converter<String, String>(handleNullAutomatically) {
      @Override
      protected String doForward(String string) {
        return "forward";
      }

      @Override
      protected String doBackward(String string) {
        return "backward";
      }
    };
  }

  public void testSerialization_identity() {
    Converter<String, String> identityConverter = Converter.identity();