case 3:
                        map.getAndIncrement(key);
                        threadSum++;
                        break;
                      case 4:
                        map.getAndDecrement(key);
                        threadSum--;
                        break;
                      case 5:
                        map.getAndAdd(key, delta);
                        threadSum += delta;

    return getAndAdd(key, 1);
  }

  /**
   * Decrements by one the value currently associated with {@code key}, and returns the old value.
   */
  @CanIgnoreReturnValue
  public long getAndDecrement(K key) {
    return getAndAdd(key, -1);
  }

  /**
   * Adds {@code delta} to the value currently associated with {@code key}, and returns the old
   * value.
   */
  @CanIgnoreReturnValue