return delta;
          }
          // atomic replaced
          continue outer;
        }

        long newValue = oldValue + delta;
        if (atomic.compareAndSet(oldValue, newValue)) {
          return newValue;
        }
        // value changed
      }
    }
  }

  /**

    assertFalse(segment.replace(key, hash, oldValue, newValue));
    assertEquals(0, segment.count);

    // same value
    table.set(index, entry);
    segment.count++;
    assertEquals(1, segment.count);
    assertSame(oldValue, segment.get(key, hash));
    assertTrue(segment.replace(key, hash, oldValue, newValue));
    assertEquals(1, segment.count);
    assertSame(newValue, segment.get(key, hash));

    assertFalse(segment.replace(key, hash, oldValue, newValue));
    assertEquals(0, segment.count);

    // same value
    table.set(index, entry);
    segment.count++;
    assertEquals(1, segment.count);
    assertSame(oldValue, segment.get(key, hash));
    assertTrue(segment.replace(key, hash, oldValue, newValue));
    assertEquals(1, segment.count);
    assertSame(newValue, segment.get(key, hash));

  }

  @CanIgnoreReturnValue
  @Override
  public boolean replace(K key, @CheckForNull V oldValue, V newValue) {
    checkNotNull(key);
    checkNotNull(newValue);
    if (oldValue == null) {
      return false;
    }
    int hash = hash(key);
    return segmentFor(hash).replace(key, hash, oldValue, newValue);
  }

  @CheckForNull
  @CanIgnoreReturnValue
  @Override

      }
    }

    @Override
    void putThread(Waiter waiter, Thread newValue) {
      UNSAFE.putObject(waiter, WAITER_THREAD_OFFSET, newValue);
    }

    @Override
    void putNext(Waiter waiter, @CheckForNull Waiter newValue) {
      UNSAFE.putObject(waiter, WAITER_NEXT_OFFSET, newValue);
    }

    /** Performs a CAS operation on the {@link #waiters} field. */
    @Override

    @CheckForNull
    public T get() {
      return value;
    }

    public void checkAndSet(@CheckForNull T expected, @CheckForNull T newValue) {
      if (value != expected) {
        throw new ConcurrentModificationException();
      }
      value = newValue;
    }

    void clear() {
      value = null;
    }
  }

  private static final class AvlNode<E extends @Nullable Object> {

                data.set(key, value);
            }

            @Override
            public <T> boolean replace(@Nonnull Key<T> key, @Nullable T oldValue, @Nullable T newValue) {
                return data.set(key, oldValue, newValue);
            }

            @Nullable
            @Override
            @SuppressWarnings("unchecked")
            public <T> T get(@Nonnull Key<T> key) {

              }

              @Override
              @ParametricNullness
              public V setValue(@ParametricNullness V newValue) {
                checkArgument(apply(getKey(), newValue));
                return super.setValue(newValue);
              }
            };
          }
        };
      }
    }

    @Override
    Set<K> createKeySet() {