I would like to get an element's int value from a String matrix. 

My task is to implement the easiest version of Uniqual (<https://www.chiark.greenend.org.uk/~sgtatham/puzzles/js/unequal.html>) with some kind of tree or graph search algorithm.

That's why I thought of implementing the table as a string, as it can contain both characters and digits. 

I have already tried this method: 
Character.isDigit(matrix[i].charAt(j))
for my issue. I guess it's not the correct way to do so.
Maybe if I get the element's char value, I could implement a simple function that checks whether it is a number or a digit or special char.