import java.util.concurrent.atomic.AtomicLong;

/**
 * One or more variables that together maintain an initially zero {@code long} sum. When updates
 * (method {@link #add}) are contended across threads, the set of variables may grow dynamically to
 * reduce contention. Method {@link #sum} (or, equivalently, {@link #longValue}) returns the current
 * total combined across the variables maintaining the sum.
 *

   * types your try block can throw when calling an overload of this method so as to avoid losing
   * the original exception type.
   *
   * <p>This method always throws, and as such should be called as {@code throw closer.rethrow(e);}
   * to ensure the compiler knows that it will throw.
   *
   * @return this method does not return; it always throws
   * @throws IOException when the given throwable is an IOException

   * result in an {@link IllegalStateException}.
   *
   * <p>The implementation of this method may not invoke the {@code hasNext}, {@code next}, or
   * {@link #peek()} methods on this instance; if it does, an {@code IllegalStateException} will
   * result.
   *
   * @return the next element if there was one. If {@code endOfData} was called during execution,

     * was called, in which case entries are sorted by value.
     *
     * <p>Prefer the equivalent method {@link #buildOrThrow()} to make it explicit that the method
     * will throw an exception if there are duplicate keys or values. The {@code build()} method
     * will soon be deprecated.
     *
     * @throws IllegalArgumentException if duplicate keys or values were added
     */
    @Override

### EventListener

Subclass [EventListener](https://square.github.io/okhttp/3.x/okhttp/okhttp3/EventListener.html) and override methods for the events you are interested in. In a successful HTTP call with no redirects or retries the sequence of events is described by this flow.

![Events Diagram](../assets/images/******@****.***)

    private ExecutorService inline = newDirectExecutorService();

    public void assertLastMethodCalled(String method) {
      assertEquals(method, lastMethodCalled);
    }

    public void assertMethodWithTimeout(String method, long timeout, TimeUnit unit) {
      assertLastMethodCalled(method + "Timeout");
      assertEquals(unit.toMillis(timeout), lastTimeoutInMillis);
    }

    @Override

  private final List<PerListenerQueue<L>> listeners =
      Collections.synchronizedList(new ArrayList<PerListenerQueue<L>>());

  /** Method reference-compatible listener event. */
  interface Event<L> {
    /** Call a method on the listener. */
    void call(L listener);
  }

  /**
   * Adds a listener that will be called using the given executor when events are later {@link

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to {@link InetAddress} instances.
 *
 * <p><b>Important note:</b> Unlike {@code InetAddress.getByName()}, the methods of this class never
 * cause DNS services to be accessed. For this reason, you should prefer these methods as much as
 * possible over their JDK equivalents whenever you are expecting to handle only IP address string

   * serialize the copy. Other methods similar to this do not implement serialization at all for
   * this reason.
   *
   * <p><b>Java 8+ users:</b> many use cases for this method are better addressed by {@link
   * java.util.stream.Stream#map}. This method is not being deprecated, but we gently encourage you
   * to migrate to streams.
   */

 *
 * <p>{@code SettableFuture} is the recommended {@code ListenableFuture} implementation when your
 * task cannot be implemented with {@link ListeningExecutorService}, the various {@link Futures}
 * utility methods, or {@link ListenableFutureTask}. Those APIs have less opportunity for developer
 * error. If your needs are more complex than {@code SettableFuture} supports, use {@link
 * AbstractFuture}, which offers an extensible version of the API.