Unique Paths

class Solution {
    public int uniquePaths(int m, int n) {
      if(m== 0 || n == 0){
        return 1;
      }
      if(m < 0 || n < 0){
        return 0;
      }
      int[][] cache = new int[m][n];
      for(int i = 0; i<m; i++){
          for(int j = 0; j<n; j++){
            if(i == 0 || j ==0){
                cache[i][j]= 1;
            }else{
                cache[i][j] = cache[i-1][j] + cache[i][j-1];
            }
      }
    }
    return cache[m-1][n-1];
    }
}