*
   * @param index the index of the stripe to return; must be in {@code [0...size())}
   * @return the stripe at the specified index
   */
  public abstract L getAt(int index);

  /**
   * Returns the index to which the given key is mapped, so that getAt(indexFor(key)) == get(key).
   */
  abstract int indexFor(Object key);

  /** Returns the total number of stripes in this instance. */
  public abstract int size();

    Set<Object> observed = Sets.newIdentityHashSet(); // for the sake of weakly referenced locks.
    // this gets the stripes with #getAt(index)
    for (int i = 0; i < striped.size(); i++) {
      Object object = striped.getAt(i);
      assertThat(object).isNotNull();
      assertThat(striped.getAt(i)).isSameInstanceAs(object); // idempotent
      observed.add(object);
    }

    Set<Object> observed = Sets.newIdentityHashSet(); // for the sake of weakly referenced locks.
    // this gets the stripes with #getAt(index)
    for (int i = 0; i < striped.size(); i++) {
      Object object = striped.getAt(i);
      assertThat(object).isNotNull();
      assertThat(striped.getAt(i)).isSameInstanceAs(object); // idempotent
      observed.add(object);
    }

    }

    /**
     * Returns the value at the specified index.
     *
     * @param index
     *            the index
     * @return the value at the specified index
     */
    public V getAt(final int index) {
        return getEntryAt(index).getValue();
    }

    /**
     * Returns the key at the specified index.
     *
     * @param index
     *            the index