}

  public void testBuilder_withMutableCell() {
    ImmutableTable.Builder<Character, Integer, String> builder = new ImmutableTable.Builder<>();

    final StringHolder holder = new StringHolder();
    holder.string = "foo";
    Table.Cell<Character, Integer, String> mutableCell =
        new Tables.AbstractCell<Character, Integer, String>() {
          @Override
          public Character getRowKey() {

    return (nullableReference == null) ? Optional.<T>absent() : new Present<T>(nullableReference);
  }

  Optional() {}

  /**
   * Returns {@code true} if this holder contains a (non-null) instance.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> no differences.
   */
  public abstract boolean isPresent();

  /**

 * {@link #writeTo} and {@link #readFrom} methods. Both serialized forms will continue to be
 * supported by future versions of this library. However, serial forms generated by newer versions
 * of the code may not be readable by older versions of the code (e.g., a serialized Bloom filter
 * generated today may <i>not</i> be readable by a binary that was compiled 6 months ago).
 *

     * Closeable}. (For more about the flavors, see <a
     * href="https://github.com/google/guava#adding-guava-to-your-build">Adding Guava to your
     * build</a>.)
     *
     * <p>Be careful when targeting an older SDK than you are building against (most commonly when
     * building for Android): Ensure that any object you pass implements the interface not just in

    }

    private static final long serialVersionUID = 5;
  }

  public void testMutableValues() {
    IntHolder holderA = new IntHolder(1);
    IntHolder holderB = new IntHolder(2);
    Map<String, IntHolder> map = ImmutableSortedMap.of("a", holderA, "b", holderB);
    holderA.value = 3;
    assertTrue(map.entrySet().contains(Maps.immutableEntry("a", new IntHolder(3))));

  }

  public void testBuilder_withMutableCell() {
    ImmutableTable.Builder<Character, Integer, String> builder = new ImmutableTable.Builder<>();

    final StringHolder holder = new StringHolder();
    holder.string = "foo";
    Table.Cell<Character, Integer, String> mutableCell =
        new Tables.AbstractCell<Character, Integer, String>() {
          @Override
          public Character getRowKey() {

            failFormat("expected divide(%s, %s, %s) = %s; got %s", p, q, mode, expected, actual);
          }
        }
      }
    }
  }

  @GwtIncompatible // TODO
  @AndroidIncompatible // Bug in older versions of Android we test against, since fixed.
  public void testDivNonZeroExact() {
    for (long p : NONZERO_LONG_CANDIDATES) {
      for (long q : NONZERO_LONG_CANDIDATES) {

    @ParametricNullness
    public T get() {
      // Another variant of Double Checked Locking.
      //
      // We use two volatile reads. We could reduce this to one by
      // putting our fields into a holder class, but (at least on x86)
      // the extra memory consumption and indirection are more
      // expensive than the extra volatile reads.
      long nanos = expirationNanos;
      long now = System.nanoTime();