* undocumented and subject to change.
   */
  public static <R, C, V> ImmutableTable<R, C, V> copyOf(
      Table<? extends R, ? extends C, ? extends V> table) {
    if (table instanceof ImmutableTable) {
      @SuppressWarnings("unchecked")
      ImmutableTable<R, C, V> parameterizedTable = (ImmutableTable<R, C, V>) table;
      return parameterizedTable;
    } else {
      return copyOf(table.cellSet());

  public void testBuilder_withImmutableCell() {
    ImmutableTable.Builder<Character, Integer, String> builder = new ImmutableTable.Builder<>();
    assertEquals(
        ImmutableTable.of('a', 1, "foo"), builder.put(immutableCell('a', 1, "foo")).build());
  }

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

          .put(BiMap.class, ImmutableBiMap.of())
          .put(ImmutableBiMap.class, ImmutableBiMap.of())
          .put(Table.class, ImmutableTable.of())
          .put(ImmutableTable.class, ImmutableTable.of())
          .put(RowSortedTable.class, Tables.unmodifiableRowSortedTable(TreeBasedTable.create()))
          .put(ClassToInstanceMap.class, ImmutableClassToInstanceMap.builder().build())

      new SecretKeySpec("secret key".getBytes(UTF_8), "HmacSHA512");

  // From http://docs.oracle.com/javase/7/docs/technotes/guides/security/StandardNames.html#Mac
  private static final ImmutableTable<String, SecretKey, HashFunction> ALGORITHMS =
      new ImmutableTable.Builder<String, SecretKey, HashFunction>()
          .put("HmacMD5", MD5_KEY, Hashing.hmacMd5(MD5_KEY))
          .put("HmacSHA1", SHA1_KEY, Hashing.hmacSha1(SHA1_KEY))

    assertTrue(ArbitraryInstances.get(SortedSetMultimap.class).isEmpty());
    assertEquals(ImmutableTable.of(), ArbitraryInstances.get(Table.class));
    assertEquals(ImmutableTable.of(), ArbitraryInstances.get(ImmutableTable.class));
    assertTrue(ArbitraryInstances.get(RowSortedTable.class).isEmpty());
    assertEquals(ImmutableBiMap.of(), ArbitraryInstances.get(BiMap.class));

          .put(BiMap.class, ImmutableBiMap.of())
          .put(ImmutableBiMap.class, ImmutableBiMap.of())
          .put(Table.class, ImmutableTable.of())
          .put(ImmutableTable.class, ImmutableTable.of())
          .put(RowSortedTable.class, Tables.unmodifiableRowSortedTable(TreeBasedTable.create()))
          .put(ClassToInstanceMap.class, ImmutableClassToInstanceMap.builder().build())

  private static final String TQBFJOTLDP = "The quick brown fox jumps over the lazy dog.";

  private static final ImmutableTable<HashFunction, String, String> KNOWN_HASHES =
      ImmutableTable.<HashFunction, String, String>builder()
          .put(Hashing.adler32(), "", "01000000")
          .put(Hashing.adler32(), TQBFJOTLD, "da0fdc5b")

        if (contents.isEmpty()) {
          return ImmutableTable.of();
        } else {
          return ArrayTable.create(contents);
        }
      }
    },
    ImmutableTableImpl {
      @Override
      <R extends Comparable<R>, C extends Comparable<C>, V> Table<R, C, V> create(
          Table<R, C, V> contents) {
        return ImmutableTable.copyOf(contents);
      }
    };

        if (contents.isEmpty()) {
          return ImmutableTable.of();
        } else {
          return ArrayTable.create(contents);
        }
      }
    },
    ImmutableTableImpl {
      @Override
      <R extends Comparable<R>, C extends Comparable<C>, V> Table<R, C, V> create(
          Table<R, C, V> contents) {
        return ImmutableTable.copyOf(contents);
      }
    };

 * not be modifiable. When modification isn't supported, those methods will throw an {@link
 * UnsupportedOperationException}.
 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableTable}
 *   <li>{@link HashBasedTable}
 *   <li>{@link TreeBasedTable}
 *   <li>{@link ArrayTable}
 *   <li>{@link Tables#newCustomTable Tables.newCustomTable}
 * </ul>
 *