void put(R row, C column, V value, BinaryOperator<V> merger) {
      MutableCell<R, C, V> oldCell = table.get(row, column);
      if (oldCell == null) {
        MutableCell<R, C, V> cell = new MutableCell<>(row, column, value);
        insertionOrder.add(cell);
        table.put(row, column, cell);
      } else {
        oldCell.merge(value, merger);
      }
    }

things you should know about contributing:

1.  API changes require discussion, use cases, etc. Code comes later.
2.  Pull requests are great for small fixes for bugs, documentation, etc.
3.  Pull requests are not merged directly into the master branch.
4.  Code contributions require signing a Google CLA.

API changes
-----------

We make changes to Guava's public [APIs][], including adding new APIs, very

import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import junit.framework.TestCase;

// TODO(cpovirk): Should this be merged into UninterruptiblesTest?
/**
 * Unit test for {@link Uninterruptibles#getUninterruptibly}
 *
 * @author Kevin Bourrillion
 * @author Chris Povirk
 */
public class UninterruptibleFutureTest extends TestCase {

@GwtCompatible(emulated = true)
@J2ktIncompatible // Super-sourced
@ElementTypesAreNonnullByDefault
abstract class GwtFluentFutureCatchingSpecialization<V extends @Nullable Object>
    extends AbstractFuture<V> {
  /*
   * This server copy of the class is empty. The corresponding GWT copy contains alternative
   * versions of catching() and catchingAsync() with slightly different signatures from the ones
   * found in FluentFuture.java.
   */

   *
   * @param element the element to prepend to the front of {@code array}
   * @param array the array of elements to append
   * @return an array whose size is one larger than {@code array}, with {@code element} occupying
   *     the first position, and the elements of {@code array} occupying the remaining elements.
   */

   * map of public suffixes. The encoded trie string may be broken into multiple chunks to avoid the
   * 64k limit on string literal size. In-memory strings can be much larger (2G).
   */
  static ImmutableMap<String, PublicSuffixType> parseTrie(CharSequence... encodedChunks) {
    String encoded = DIRECT_JOINER.join(encodedChunks);
    return parseFullString(encoded);
  }

 * features}, the features supported by the iterator; and {@code expectedElements}, the elements the
 * iterator should return in order.
 *
 * <p>The items in {@code elementsToInsert} will be repeated if {@code steps} is larger than the
 * number of provided elements.
 *
 * @author Chris Povirk
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ListIteratorTester<E extends @Nullable Object>

 * features}, the features supported by the iterator; and {@code expectedElements}, the elements the
 * iterator should return in order.
 *
 * <p>The items in {@code elementsToInsert} will be repeated if {@code steps} is larger than the
 * number of provided elements.
 *
 * @author Chris Povirk
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ListIteratorTester<E extends @Nullable Object>

  }

  /**
   * Configures the given map maker to use weak keys, if possible; does nothing otherwise (i.e., in
   * GWT). This is sometimes acceptable, when only server-side code could generate enough volume
   * that reclamation becomes important.
   */
  @J2ktIncompatible
  static MapMaker tryWeakKeys(MapMaker mapMaker) {
    return mapMaker.weakKeys();
  }

 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>
 * new EqualsTester()
 *     .addEqualityGroup(new User("page"), new User("page"))
 *     .addEqualityGroup(new User("sergey"))
 *     .testEquals();
 * </pre>
 *
 * <p>This tests:
 *
 * <ul>
 *   <li>comparing each object against itself returns true
 *   <li>comparing each object against null returns false