*     rateLimiter.acquire(); // may wait
 *     executor.execute(task);
 *   }
 * }
 * }</pre>
 *
 * <p>As another example, imagine that we produce a stream of data, and we want to cap it at 5kb per
 * second. This could be accomplished by requiring a permit per byte, and specifying a rate of 5000
 * permits per second:
 *
 * <pre>{@code
 * final RateLimiter rateLimiter = RateLimiter.create(5000.0); // rate = 5000 permits per second

 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;
import static junit.framework.Assert.assertEquals;

   * ForwardingMultiset#containsAll}, {@link ForwardingMultiset#count}, {@link
   * ForwardingMultiset#isEmpty}, the {@link Set#size} and {@link Set#iterator} methods of {@link
   * ForwardingMultiset#entrySet}, and {@link ForwardingMultiset#remove(Object, int)}. In many
   * situations, you may wish to override {@link ForwardingMultiset#elementSet} to forward to this

  }

  /**
   * Returns a {@code Collector} accumulating entries into an {@code ImmutableSetMultimap}. Each
   * input element is mapped to a key and a stream of values, each of which are put into the
   * resulting {@code Multimap}, in the encounter order of the stream and the encounter order of the
   * streams of values.
   *
   * <p>Example:
   *
   * <pre>{@code

 *       #toString} behavior you expect
 *   <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to
 *       hunt through classes like {@link Arrays} and {@link Ints} for them.
 *   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.

   *
   * @param string the string to test and possibly return
   * @return {@code string} itself if it is non-null; {@code ""} if it is null
   */
  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

 *       #toString} behavior you expect.
 *   <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to
 *       hunt through classes like {@link Arrays} and {@link Doubles} for them.
 *   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.

     *
     * <p>This method is used when testing iterators without a known ordering. We poll the target
     * iterator's next element and pass it to the reference iterator through this method so it can
     * return the same element. This enables the assertion to pass and the reference iterator to
     * properly update its state.
     */
    void promoteToNext(E e) {
      if (nextElements.remove(e)) {

    return CollectCollectors.toImmutableList();
  }

  /**
   * Returns the empty immutable list. This list behaves and performs comparably to {@link
   * Collections#emptyList}, and is preferable mainly for consistency and maintainability of your
   * code.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */

@ElementTypesAreNonnullByDefault
public final class Suppliers {
  private Suppliers() {}

  /**
   * Returns a new supplier which is the composition of the provided function and supplier. In other
   * words, the new supplier's value will be computed by retrieving the value from {@code supplier},
   * and then applying {@code function} to that value. Note that the resulting supplier will not
   * call {@code supplier} or invoke {@code function} until it is called.
   */