swap(array, from, to);
        }
        return array[k];
      } else {
        int midIndex = (from + to) >>> 1;
        // Choose the median of the elements at the from, to and mid indexes,
        // and rearrange so that array[from]<=array[from+1], and
        // array[to] => array[from + 1].

        swap(array, midIndex, from + 1);

        if (array[from] > array[to]) {

          swap(array, from, to);
        }
        return array[k];
      } else {
        int midIndex = (from + to) >>> 1;
        // Choose the median of the elements at the from, to and mid indexes,
        // and rearrange so that array[from]<=array[from+1], and
        // array[to] => array[from + 1].

        swap(array, midIndex, from + 1);

        if (array[from] > array[to]) {

    assertThat(Booleans.concat(ARRAY_FALSE)).isEqualTo(ARRAY_FALSE);
    assertThat(Booleans.concat(ARRAY_FALSE)).isNotSameInstanceAs(ARRAY_FALSE);
    assertThat(Booleans.concat(EMPTY, ARRAY_FALSE, EMPTY)).isEqualTo(ARRAY_FALSE);
    assertThat(Booleans.concat(ARRAY_FALSE, ARRAY_FALSE, ARRAY_FALSE))
        .isEqualTo(new boolean[] {false, false, false});
    assertThat(Booleans.concat(ARRAY_FALSE, ARRAY_FALSE_TRUE))

    assertThat(Booleans.concat(ARRAY_FALSE)).isEqualTo(ARRAY_FALSE);
    assertThat(Booleans.concat(ARRAY_FALSE)).isNotSameInstanceAs(ARRAY_FALSE);
    assertThat(Booleans.concat(EMPTY, ARRAY_FALSE, EMPTY)).isEqualTo(ARRAY_FALSE);
    assertThat(Booleans.concat(ARRAY_FALSE, ARRAY_FALSE, ARRAY_FALSE))
        .isEqualTo(new boolean[] {false, false, false});
    assertThat(Booleans.concat(ARRAY_FALSE, ARRAY_FALSE_TRUE))

  private final int end; // exclusive

  private ImmutableIntArray(int[] array) {
    this(array, 0, array.length);
  }

  private ImmutableIntArray(int[] array, int start, int end) {
    this.array = array;
    this.start = start;
    this.end = end;
  }

  /** Returns the number of values in this array. */
  public int length() {
    return end - start;
  }

  private final int end; // exclusive

  private ImmutableDoubleArray(double[] array) {
    this(array, 0, array.length);
  }

  private ImmutableDoubleArray(double[] array, int start, int end) {
    this.array = array;
    this.start = start;
    this.end = end;
  }

  /** Returns the number of values in this array. */
  public int length() {
    return end - start;
  }

  }

  /**
   * @return an array of the proper size with {@code null} as the key of the middle element.
   */
  protected Entry<K, V>[] createArrayWithNullKey() {
    Entry<K, V>[] array = createSamplesArray();
    int nullKeyLocation = getNullLocation();
    Entry<K, V> oldEntry = array[nullKeyLocation];
    array[nullKeyLocation] = Helpers.mapEntry(null, oldEntry.getValue());
    return array;
  }

  /**

    if (toLessThanMid == midLessThanFrom) {
      // Either array[to] < array[mid] < array[from] or array[from] <= array[mid] <= array[to].
      swap(array, mid, from);
    } else if (toLessThanMid != toLessThanFrom) {
      // Either array[from] <= array[to] < array[mid] or array[mid] <= array[to] < array[from].
      swap(array, from, to);
    }

          array[i] = counter.getAndIncrement();
        }
        builder.addAll(ImmutableLongArray.copyOf(array));
      }
    },
    ADD_LARGER_ARRAY {
      @Override
      void doIt(ImmutableLongArray.Builder builder, AtomicLong counter) {
        long[] array = new long[RANDOM.nextInt(200) + 200];
        for (int i = 0; i < array.length; i++) {
          array[i] = counter.getAndIncrement();
        }

      }
    },
    ADD_ARRAY {
      @Override
      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        double[] array = new double[RANDOM.nextInt(10)];
        for (int i = 0; i < array.length; i++) {
          array[i] = counter.getAndIncrement();
        }
        builder.addAll(array);
      }
    },
    ADD_COLLECTION {
      @Override