So is this checkers or sudoku?
How would I do that
pseudocode
for(i=0;i<9;i++){ //row
maybe an arraylist of horizontals
for(j=0;j<9;j++){ // columns
//check for distinct row value
if(the arraylist of horizontals does not contain something?)
System.out.println("no distinct num")
what happened when you tried it? Does it solve the problem?
Are the first 9 in the top row? Second 9 in the second row? last 9 end up in the last row? If all 3 are yes then it seems right so far.
Looks to me like the only thing you are missing is the confidence to move forward.