docs: protected void extendArray(int k) {
      // size + 1 could overflow
      if (this.size + k > this.keys.length) {
        int newCapacity;
        if (this.keys.length < 1024) {
          newCapacity = 2 * (this.size + k);
        } else {
          newCapacity = 5 * (this.size + k) / 4;
        }
        this.keys = Arrays.copyOf(this.keys, newCapacity);
        this.values = Arrays.copyOf(this.values, newCapacity);
      }
    }