Having trouble with counting program

Question

I made a program to count the number of lines and number of characters from an input file. My program (below) successfully does that, as far as I know. I must also call a function to count the number of occurences of a certain letter, in this case 'a'. I can compile with no errors, but when I execute, it says there is a problem at line 1961, which is the next to last character in my input file. It says it's out of bounds....??? Thanks for the help.
import java.util.*;
public class Count{
     public static void main(String[] args){
          Scanner keyBoard = new Scanner(System.in);
          String line;
          String totallines = "";
          int countline = 0;
          int countchar = 0;
          int totalcharacters = 0;
          int totallength = 0;
          while(keyBoard.hasNext()){
               line = keyBoard.nextLine();
               String lower = line.toLowerCase();
               countline++;
               int len = line.length();
               totallength = totallength + len;
               totalcharacters = totalcharacters + countchar;
               totallines = totallines + line;          
          totallength = totallength + 1;
          System.out.println(countline);
          System.out.println(totallength);
          countChar('a', totallines, totallength);
     public static int countChar(char ch, String s, int totallength){
          int countcharacter = 0;
          for (int k = totallength-1; k >= 0; k--){
               if (s.charAt(k) == ch){
                    countcharacter++;
          System.out.println(countcharacter);
          return countcharacter;
}

Answer 1

--...OutOfBounds exception means to indicate that an array has been accessed with an illegal index. The index is either negative or greater than or equal to the size of the array.
--it also applies if you're goin to accessed your String.. try to double check all your loops that has an access to your strings....