* 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(

import java.util.List;
import java.util.Set;
import javax.annotation.CheckForNull;

/**
 * An implementation of {@link ImmutableTable} holding an arbitrary number of cells.
 *
 * @author Gregory Kick
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class RegularImmutableTable<R, C, V> extends ImmutableTable<R, C, V> {
  RegularImmutableTable() {}

  abstract Cell<R, C, V> getCell(int iterationIndex);

  @Override

        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);
      }
    };

 * which will still appear when iterating over the table's contents in a foreach loop or a call to a
 * null-hostile method like {@link ImmutableTable#copyOf}. For alternatives, please see <a
 * href="https://github.com/google/guava/wiki/NewCollectionTypesExplained#table">the wiki</a>.
 *