};
  }

  /**
   * Combines two iterators into a single iterator. The returned iterator iterates across the
   * elements in {@code a}, followed by the elements in {@code b}. The source iterators are not
   * polled until necessary.
   *
   * <p>The returned iterator supports {@code remove()} when the corresponding input iterator
   * supports it.
   */
  public static <T extends @Nullable Object> Iterator<T> concat(

  }

  /**
   * Combines two iterables into a single iterable. The returned iterable has an iterator that
   * traverses the elements in {@code a}, followed by the elements in {@code b}. The source
   * iterators are not polled until necessary.
   *
   * <p>The returned iterable's iterator supports {@code remove()} when the corresponding input
   * iterator supports it.
   *

 *
 * <p>Subscribers should not, in general, throw. If they do, the EventBus will catch and log the
 * exception. This is rarely the right solution for error handling and should not be relied upon; it
 * is intended solely to help find problems during development.
 *
 * <p>The EventBus guarantees that it will not call a subscriber method from multiple threads
 * simultaneously, unless the method explicitly allows it by bearing the {@link

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Outer class that exists solely to let us write {@code Partially.GwtIncompatible} instead of plain
 * {@code GwtIncompatible}. This is more accurate for {@link Futures#catching}, which is available
 * under GWT but with a slightly different signature.
 *

  /**
   * Returns a fluent iterable that combines two iterables. The returned iterable has an iterator
   * that traverses the elements in {@code a}, followed by the elements in {@code b}. The source
   * iterators are not polled until necessary.
   *
   * <p>The returned iterable's iterator supports {@code remove()} when the corresponding input
   * iterator supports it.
   *
   * <p><b>{@code Stream} equivalent:</b> {@link Stream#concat}.

    };
  }

  /**
   * Combines two iterators into a single iterator. The returned iterator iterates across the
   * elements in {@code a}, followed by the elements in {@code b}. The source iterators are not
   * polled until necessary.
   *
   * <p>The returned iterator supports {@code remove()} when the corresponding input iterator
   * supports it.
   */
  public static <T extends @Nullable Object> Iterator<T> concat(

    throw new UnsupportedOperationException();
  }

  /**
   * Accumulates statistics during the operation of a {@link Cache} for presentation by {@link
   * Cache#stats}. This is solely intended for consumption by {@code Cache} implementors.
   *
   * @since 10.0
   */
  public interface StatsCounter {
    /**