code: void putAll(BitArray array) {
      assert data.length == array.data.length : "BitArrays must be of equal length when merging";
      long bitCount = 0;
      for (int i = 0; i < data.length; i++) {
        data[i] |= array.data[i];
        bitCount += Long.bitCount(data[i]);
      }
      this.bitCount = bitCount;
    }
docs: Combines the two BitArrays using bitwise OR.