return file(new File(first), more);
  }

  /** Returns a {@code File} object for the given path parts. */
  private static File file(File first, String... more) {
    // not very efficient, but should definitely be correct
    File file = first;
    for (String name : more) {
      file = new File(file, name);
    }
    return file;
  }

      }
    }
  }

  /** Returns the {@code Class} object of arrays with {@code componentType}. */
  static Class<?> getArrayClass(Class<?> componentType) {
    // TODO(user): This is not the most efficient way to handle generic
    // arrays, but is there another way to extract the array class in a
    // non-hacky way (i.e. using String value class names- "[L...")?
    return Array.newInstance(componentType, 0).getClass();

          int actual = LongMath.lessThanBranchFree(x, y);
          assertEquals(expected, actual);
        }
      }
    }
  }

  // Throws an ArithmeticException if "the simple implementation" of binomial coefficients overflows
  @GwtIncompatible // TODO
  private long simpleBinomial(int n, int k) {
    long accum = 1;
    for (int i = 0; i < k; i++) {
      accum = LongMath.checkedMultiply(accum, n - i);
      accum /= i + 1;

   * Reader#skip(long) skip} to the end of the stream, and return the total number of chars that
   * were skipped.
   *
   * <p>Note that for sources that implement {@link #lengthIfKnown} to provide a more efficient
   * implementation, it is <i>possible</i> that this method will return a different number of chars
   * than would be returned by reading all of the chars.
   *

   * Reader#skip(long) skip} to the end of the stream, and return the total number of chars that
   * were skipped.
   *
   * <p>Note that for sources that implement {@link #lengthIfKnown} to provide a more efficient
   * implementation, it is <i>possible</i> that this method will return a different number of chars
   * than would be returned by reading all of the chars.
   *

 *     .url("http://publicobject.com/helloworld.txt")
 *     .build();
 * ```
 *
 * If it is only necessary to force a cached response to be validated by the server, use the more
 * efficient `max-age=0` directive instead:
 *
 * ```java
 * Request request = new Request.Builder()
 *     .cacheControl(new CacheControl.Builder()
 *         .maxAge(0, TimeUnit.SECONDS)
 *         .build())

    assertEquals("", is('a').retainFrom(""));
  }

  public void testPrecomputedOptimizations() {
    // These are testing behavior that's never promised by the API.
    // Some matchers are so efficient that it is a waste of effort to
    // build a precomputed version.
    CharMatcher m1 = is('x');
    assertSame(m1, m1.precomputed());
    assertEquals(m1.toString(), m1.precomputed().toString());

        }
        return true; // that.size() == this.size()
      }
    }

    /**
     * Returns a lower bound for {@link #size()} based on the sizes of the backing sets.
     *
     * <p>This is more efficient than {@link #size()}, which iterates over the entire {@link
     * SetView}.
     */
    abstract int minSize();

    /**

    assertEquals("", is('a').retainFrom(""));
  }

  public void testPrecomputedOptimizations() {
    // These are testing behavior that's never promised by the API.
    // Some matchers are so efficient that it is a waste of effort to
    // build a precomputed version.
    CharMatcher m1 = is('x');
    assertSame(m1, m1.precomputed());
    assertEquals(m1.toString(), m1.precomputed().toString());

  }

  /**
   * Creates an empty multiset containing the given initial elements, sorted according to the
   * elements' natural order.
   *
   * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}.
   *
   * <p>The type specification is {@code <E extends Comparable>}, instead of the more specific