code: public void increment(int i, int j, double value)
      {
          if(Double.isNaN(value) || Double.isInfinite(value))
              throw new ArithmeticException("Can not add a value " + value);
          set(i, j, get(i, j)+value);
      }
docs: Alters the current matrix at index <i>(i,j)</i> to be equal to
  <i>A<sub>i,j</sub> = A<sub>i,j</sub> + value</i>
  @param i the row, starting from 0
  @param j the column, starting from 0
  @param value the value to add to the matrix coordinate