if (atomic == null) {
        atomic = map.putIfAbsent(key, new AtomicLong(delta));
        if (atomic == null) {
          return delta;
        }
        // atomic is now non-null; fall through
      }

      while (true) {
        long oldValue = atomic.get();
        if (oldValue == 0L) {
          // don't compareAndSet a zero
          if (map.replace(key, atomic, new AtomicLong(delta))) {

import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import javax.annotation.CheckForNull;

/**
 * A map-like data structure that wraps a backing map and caches values while iterating through
 * {@link #unmodifiableKeySet()}. By design, the cache is cleared when this structure is mutated. If
 * this structure is never mutated, it provides a thread-safe view of the backing map.
 *

 * @since 15.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class Escapers {
  private Escapers() {}

  /**
   * Returns an {@link Escaper} that does no escaping, passing all character data through unchanged.
   */
  public static Escaper nullEscaper() {
    return NULL_ESCAPER;
  }

  // An Escaper that efficiently performs no escaping.

@GwtIncompatible
public class PackageSanityTests extends AbstractPackageSanityTests {
  public PackageSanityTests() {
    // package private classes like FunctionalEquivalence are tested through the public API.
    publicApiOnly();
  }

 *
 * @author Ben Yu
 */

public class PackageSanityTests extends AbstractPackageSanityTests {
  public PackageSanityTests() {
    publicApiOnly(); // Many package-private classes are tested through the public API.
    setDefault(DiscreteDomain.class, DiscreteDomain.integers());
  }

    };
  }

  /**
   * Uses a hash table to map keys to value collections.
   *
   * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
   * Multimap#asMap()} will iterate through the keys in the order that they were first added to the
   * multimap, save that if all values associated with a key are removed and then the key is added
   * back into the multimap, that key will come last in the key iteration order.

import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests creation (typically through a constructor or static factory
 * method) of a list. Can't be invoked directly; please see {@link
 * com.google.common.collect.testing.ListTestSuiteBuilder}.
 *
 * @author Chris Povirk
 */
@GwtCompatible

   * characters, even though <a href="https://goo.gl/e7E0In">many of these are accepted in modern
   * URLs</a>.
   *
   * <p>When escaping a String, the following rules apply:
   *
   * <ul>
   *   <li>The alphanumeric characters "a" through "z", "A" through "Z" and "0" through "9" remain
   *       the same.

 * #delegate()} method must be overridden to return the instance being decorated.
 *
 * <p>This class does <i>not</i> forward the {@code hashCode} and {@code equals} methods through to
 * the backing object, but relies on {@code Object}'s implementation. This is necessary to preserve
 * the symmetry of {@code equals}. Custom definitions of equality are usually based on an interface,

    assertTrue(getMap().inverse().containsKey(null));
    assertNull(getMap().get(k1()));
    assertEquals(k1(), getMap().inverse().get(null));
    assertEquals(1, getMap().size());
  }

  // nb: inverse is run through its own entire suite

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(ZERO)
  public void testInversePut() {
    getMap().put(k0(), v0());
    getMap().inverse().put(v1(), k1());