* apps use <a href="https://dagger.dev">Dagger</a>. For server code, common options include <a
 * href="https://github.com/google/guice/wiki/Motivation">Guice</a> and <a
 * href="https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#beans-introduction">Spring</a>.
 * Frameworks typically offer a way to register multiple listeners independently and then request

   */
  public static String nullToEmpty(@CheckForNull String string) {
    return Platform.nullToEmpty(string);
  }

  /**
   * Returns the given string if it is nonempty; {@code null} otherwise.
   *
   * @param string the string to test and possibly return
   * @return {@code string} itself if it is nonempty; {@code null} if it is empty or null
   */
  @CheckForNull

    Set<String> set = of("a", "b", "c", "d", "e", "f", "g", "h");
    assertEquals(Sets.newHashSet("a", "b", "c", "d", "e", "f", "g", "h"), set);
  }

  public void testCopyOf_emptyArray() {
    String[] array = new String[0];
    Set<String> set = copyOf(array);
    assertEquals(Collections.<String>emptySet(), set);
    assertSame(this.<String>of(), set);
  }

  public void testCopyOf_arrayOfOneElement() {

    Set<String> set = of("a", "b", "c", "d", "e", "f", "g", "h");
    assertEquals(Sets.newHashSet("a", "b", "c", "d", "e", "f", "g", "h"), set);
  }

  public void testCopyOf_emptyArray() {
    String[] array = new String[0];
    Set<String> set = copyOf(array);
    assertEquals(Collections.<String>emptySet(), set);
    assertSame(this.<String>of(), set);
  }

  public void testCopyOf_arrayOfOneElement() {

  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";

        Gender gender,
        Integer integer,
        int i,
        String string,
        CharSequence charSequence,
        List<String> list,
        ImmutableList<Integer> immutableList,
        Map<String, Integer> map,
        ImmutableMap<String, String> immutableMap,
        Set<String> set,
        ImmutableSet<Integer> immutableSet,
        SortedSet<Number> sortedSet,

    @SuppressWarnings("GuardedBy")
    @Override
    public String toString() {
      Runnable currentlyRunning = task;
      if (currentlyRunning != null) {
        return "SequentialExecutorWorker{running=" + currentlyRunning + "}";
      }
      return "SequentialExecutorWorker{state=" + workerRunningState + "}";
    }
  }

  @Override
  public String toString() {

      return Objects.hashCode(function, supplier);
    }

    @Override
    public String toString() {
      return "Suppliers.compose(" + function + ", " + supplier + ")";
    }

    private static final long serialVersionUID = 0;
  }

  /**
   * Returns a supplier which caches the instance retrieved during the first call to {@code get()}
   * and returns that value on subsequent calls to {@code get()}. See: <a

   *     arbitrary past or present time
   */
  abstract long reserveEarliestAvailable(int permits, long nowMicros);

  @Override
  public String toString() {
    return String.format(Locale.ROOT, "RateLimiter[stableRate=%3.1fqps]", getRate());
  }

  abstract static class SleepingStopwatch {
    /** Constructor for use by subclasses. */
    protected SleepingStopwatch() {}

    private final String toString;

    protected Stimulus(String toString) {
      this.toString = toString;
    }

    /**
     * Send this stimulus to both iterators and return normally only if both produce the same
     * response.
     */
    abstract void executeAndCompare(ListIterator<E> reference, T target);

    @Override
    public String toString() {
      return toString;