How can I measure the length of a 2D array?

Question

The grades [] [] is a 2D array and i want to return the length of the second dimension, that is 8.
And grades[].length doesn't work, so what's the problem?
Thanks!!!!!!!!
  static String [] [] grades={{"A","B","B","D","D","C","A","F"},                         
                                               {"F","B","C","B","A","D","B","B"},
                                               {"C","C","E","E","F","C","B","A"},
                                               {"C","D","E","D","B","C","D","E"}};
     static int marks [] []=new int[grades.length] [grades[].length];  // why doesn't it work??

Answer 1

static String [] [] grades={{"A","B","B","D","D","C","A","F"},                         
                                               {"F","B","C","B","A","D","B","B"},
                                               {"C","C","E","E","F","C","B","A"},
                                               {"C","D","E","D","B","C","D","E"}};
static int[][] integer_grades=convertToInt(grades);
static int[][] convertToInt(String[][] grades)
int[][] grade_ints = new int[grades.length][];
for (int j=0; j<grades.length;j++)
       grade_ints[j]=new int[grades[j].length];
       for (int k=0; k<grades[j].length; k++)
                grade_ints[j][k]=convertToInt(grades[j][k]);
return grade_ints;
static int convertToInt(String s)
   if (s.equals("A")) {return 5;}
   else if (s.equals("B")){return 4;}
   else if (s.equals("C")){return 3;}
   else if (s.equals("D")) {return 2;}
   else if (s.equals("F")) {return 1;}
   return 0;
}Should work--didn't test it though..wrote it in a hurry...