code: public void ensureCapacity (int additionalCapacity) {
  		int sizeNeeded = size + additionalCapacity;
  		if (sizeNeeded >= threshold) resize(ObjectMap.nextPowerOfTwo((int)(sizeNeeded / loadFactor)));
  	}
docs: Increases the size of the backing array to acommodate the specified number of additional items. Useful before adding many
  items to avoid multiple backing array resizes.