final L listener;
    final Executor executor;

    @GuardedBy("this")
    final Queue<ListenerCallQueue.Event<L>> waitQueue = new ArrayDeque<>();

    @GuardedBy("this")
    final Queue<Object> labelQueue = new ArrayDeque<>();

    @GuardedBy("this")
    boolean isThreadScheduled;

    PerListenerQueue(L listener, Executor executor) {

import static com.google.common.base.Throwables.throwIfUnchecked;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jspecify.annotations.NullMarked;

import static com.google.common.base.Throwables.throwIfUnchecked;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jspecify.annotations.NullMarked;

   * one of three states:
   *   - Active: shutdown == false
   *   - Shutdown: runningTasks > 0 and shutdown == true
   *   - Terminated: runningTasks == 0 and shutdown == true
   */
  @GuardedBy("lock")
  private int runningTasks = 0;

  @GuardedBy("lock")
  private boolean shutdown = false;

  @Override
  public void execute(Runnable command) {
    startTask();
    try {
      command.run();
    } finally {

        }
        return toReturn;
      }

      @GuardedBy("lock")
      /*
       * The GuardedBy checker warns us that we're not holding cancellationDelegate.lock. But in
       * fact we are holding it because it is the same as this.lock, which we know we are holding,
       * thanks to @GuardedBy above. (cancellationDelegate.lock is initialized to this.lock in the

    static final Logger log = Logger.getLogger(NewExecutionListQueue.class.getName());

    @GuardedBy("this")
    private @Nullable RunnableExecutorPair head;

    @GuardedBy("this")
    private @Nullable RunnableExecutorPair tail;

    @GuardedBy("this")
    private boolean executed;

    void add(Runnable runnable, Executor executor) {

 */

package com.google.common.util.concurrent;

import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertThrows;

import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.lang.reflect.Method;
import java.net.URLClassLoader;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CancellationException;
import java.util.concurrent.Executor;

    final L listener;
    final Executor executor;

    @GuardedBy("this")
    final Queue<ListenerCallQueue.Event<L>> waitQueue = new ArrayDeque<>();

    @GuardedBy("this")
    final Queue<Object> labelQueue = new ArrayDeque<>();

    @GuardedBy("this")
    boolean isThreadScheduled;

    PerListenerQueue(L listener, Executor executor) {

    final Monitor monitor = new Monitor();

    @GuardedBy("monitor")
    final SetMultimap<State, Service> servicesByState =
        MultimapBuilder.enumKeys(State.class).linkedHashSetValues().build();

    @GuardedBy("monitor")
    final Multiset<State> states = servicesByState.keys();

    @GuardedBy("monitor")
    final IdentityHashMap<Service, Stopwatch> startupTimers = new IdentityHashMap<>();

    final Monitor monitor = new Monitor();

    @GuardedBy("monitor")
    final SetMultimap<State, Service> servicesByState =
        MultimapBuilder.enumKeys(State.class).linkedHashSetValues().build();

    @GuardedBy("monitor")
    final Multiset<State> states = servicesByState.keys();

    @GuardedBy("monitor")
    final IdentityHashMap<Service, Stopwatch> startupTimers = new IdentityHashMap<>();