*/
    FAILED,
  }

  /**
   * A listener for the various state changes that a {@link Service} goes through in its lifecycle.
   *
   * <p>All methods are no-ops by default, implementors should override the ones they care about.
   *
   * @author Luke Sandberg
   * @since 15.0 (present as an interface in 13.0)
   */
  abstract class Listener {
    /** Constructor for use by subclasses. */

  sufficient description, if applicable unit tests are added, if it is a
  reasonable contribution (meaning it is not a single liner cosmetic PR).

**2. Valid?**

-   If the PR passes all the quality checks then we go ahead and assign a
    reviewer.
-   If the PR didn't meet the validation criteria, we request for additional
    changes to be made to PR to pass quality checks and send it back or on a
    rare occasion we may reject it.

**3. Review**

   * A thread-safe cache that contains the mapping from each class to all methods in that class and
   * all super-classes, that are annotated with {@code @Subscribe}. The cache is shared across all
   * instances of this class; this greatly improves performance if multiple EventBus instances are
   * created and objects of the same class are registered on all of them.
   */
  private static final LoadingCache<Class<?>, ImmutableList<Method>> subscriberMethodsCache =

   *       collections intelligently fall back to a binary search tree if hash table collisions are
   *       detected. Rather than going to all the trouble of reimplementing this ourselves, we
   *       simply switch over to use the JDK implementation wholesale if probable hash flooding is
   *       detected, sacrificing the compactness guarantee in very rare cases in exchange for much
   *       more reliable worst-case behavior.

import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A strategy for determining whether two instances are considered equivalent, and for computing
 * hash codes in a manner consistent with that equivalence. Two examples of equivalences are the
 * {@linkplain #identity() identity equivalence} and the {@linkplain #equals "equals" equivalence}.
 *

    checkNotNull(reason);
    /*
     * All elements of `futures` are completed, or this future has already completed and read
     * `futures` into a local variable (in preparation for propagating cancellation to them). In
     * either case, no one needs to read `futures` for cancellation purposes later. (And
     * cancellation purposes are the main reason to access `futures`, as discussed in its docs.)
     */

---

Here's how to help others with questions (in discussions or issues):

### Understand the question { #understand-the-question }

* Check if you can understand what is the **purpose** and use case of the person asking.

* Then check if the question (the vast majority are questions) is **clear**.

    return key;
  }

  /**
   * Returns the current value for this system property by delegating to {@link
   * System#getProperty(String)}.
   *
   * <p>The value returned by this method is non-null except in rare circumstances:
   *
   * <ul>
   *   <li>{@link #JAVA_EXT_DIRS} was deprecated in Java 8 and removed in Java 9. We have not
   *       confirmed whether it is available under older versions.

 * #lazyWeakReadWriteLock(int) weak} {@code Striped<ReadWriteLock>}. <i>Strong</i> means that all
 * stripes (locks/semaphores) are initialized eagerly, and are not reclaimed unless {@code Striped}
 * itself is reclaimable. <i>Weak</i> means that locks/semaphores are created lazily, and they are
 * allowed to be reclaimed if nobody is holding on to them. This is useful, for example, if one

   * @throws IllegalArgumentException if not all services are {@linkplain State#NEW new} or if there
   *     are any duplicate services.
   */
  public ServiceManager(Iterable<? extends Service> services) {
    ImmutableList<Service> copy = ImmutableList.copyOf(services);
    if (copy.isEmpty()) {
      // Having no services causes the manager to behave strangely. Notably, listeners are never