code: public synchronized int addColumn(double[] column) {
          if (isFinished)
              throw new IllegalStateException(
                  "Cannot add rows to a MatrixBuilder that is finished");
          for (int r = 0; r < column.length; ++r) {
              if (column[r] != 0d) {
                  // NB: Matlab sparse format is in [col row val] format
                  //
                  // NOTE: Matlab indices start at 1, not 0, so update all the
                  // row and column values to be Matlab formatted.
                  addEntry(r + 1, curColumn + 1, column[r]);
              }
          }
          return ++curColumn;
      }
docs: {@inheritDoc}