code: public double[] getColumn(int column) {
          checkIndices(0, column);
          rowReadLock.lock();
          double[] values = new double[rows.get()];
          for (int row = 0; row < rows.get(); ++row)
              values[row] = get(row, column);
          rowReadLock.unlock();
          return values;
      }
docs: {@inheritDoc} The length of the returned column reflects the size of
  matrix at the time of the call, which may be different from earlier calls
  to {@link #rows()}