}

  /**
   * Reserves the given number of permits from this {@code RateLimiter} for future use, returning
   * the number of microseconds until the reservation can be consumed.
   *
   * @return time in microseconds to wait until the resource can be acquired, never negative
   */
  final long reserve(int permits) {
    checkPermits(permits);
    synchronized (mutex()) {

   * Encapsulates the action to be taken when a potential deadlock is encountered. Clients can use
   * one of the predefined {@link Policies} or specify a custom implementation. Implementations must
   * be thread-safe.
   *
   * @since 13.0
   */
  public interface Policy {

    /**
     * Called when a potential deadlock is encountered. Implementations can throw the given {@code
     * exception} and/or execute other desired logic.

   *
   * <ul>
   *   <li>You want to assign the same fraction of inputs to each bucket.
   *   <li>When you reduce the number of buckets, you can accept that the most recently added
   *       buckets will be removed first. More concretely, if you are dividing traffic among tasks,
   *       you can decrease the number of tasks from 15 and 10, killing off the final 5 tasks, and

   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *
   * @param collection the presumed-immutable collection

 * </h4>
 *
 * <p>Users of {@code CompletableFuture} will likely want to continue using {@code
 * CompletableFuture}. {@code FluentFuture} is targeted at people who use {@code ListenableFuture},
 * who can't use Java 8, or who want an API more focused than {@code CompletableFuture}. (If you
 * need to adapt between {@code CompletableFuture} and {@code ListenableFuture}, consider <a

   * {@code Map<T, Something>} to {@code Map<String, Something>} etc. Similarly, {@code formal} and
   * {@code actual} can be {@code Map<K, V>} and {@code Map<String, Integer>} respectively, or they
   * can be {@code E[]} and {@code String[]} respectively, or even any arbitrary combination
   * thereof.
   *

      // index * (dataset.length - 1) / scale. If there is no remainder, we can just find the value
      // whose index in the sorted dataset equals the quotient; if there is a remainder, we
      // interpolate between that and the next value.

      // Since index and (dataset.length - 1) are non-negative ints, their product can be expressed
      // as a long, without risk of overflow:

    } catch (Throwable t) {
      /*
       * This is not one of AppEngine's allowed classes, so even in Sun JDKs, this can fail with
       * a NoClassDefFoundError. Other apps might deny access to sun.misc packages.
       */
      return null;
    }
  }

  /**
   * Returns the Method that can be used to resolve an individual StackTraceElement, or null if that

    } catch (Throwable t) {
      /*
       * This is not one of AppEngine's allowed classes, so even in Sun JDKs, this can fail with
       * a NoClassDefFoundError. Other apps might deny access to sun.misc packages.
       */
      return null;
    }
  }

  /**
   * Returns the Method that can be used to resolve an individual StackTraceElement, or null if that

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code retainAll} operations on a collection. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author Chris Povirk
 */
@GwtCompatible