Array Index Out of Bounds Exception (Java)

Question

Here is my code:

public class countChar {

    public static void main(String[] args) {
        int i;
        String userInput = new String();

        userInput = Input.getString("Please enter a sentence");

        int[] total = totalChars(userInput.toLowerCase());

        for (i = 0; i < total.length; i++);
        {
            if (total[i] != 0) {
                System.out.println("Letter" + (char) ('a' + i) + " count =" + total[i]);
            }
        }
    }

    public static int[] totalChars(String userInput) {
        int[] total = new int[26];
        int i;
        for (i = 0; i < userInput.length(); i++) {
            if (Character.isLetter(userInput.charAt(i))) {
                total[userInput.charAt(i) - 'a']++;
            }
        }
        return total;
    }
}

The program's purpose is to ask the user for a string, and then count the number of times each character is used in the string.

When I go to compile the program, it works fine. When I run the program, I am able to enter a string in the popup box, but after I submit the string and press OK, I get an error, saying

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 26
at countChar.main(countChar.java:14)

I'm not completely sure what the problem is or how to fix it.

Answer 1

for ( i = 0; i < total.length; i++ );
                                    ^-- remove the semi-colon here

With this semi-colon, the loop loops until i == total.length, doing nothing, and then what you thought was the body of the loop is executed.

Answer 2

for ( i = 0; i < total.length; i++ ); // remove this
{
    if (total[i]!=0)
        System.out.println( "Letter" + (char)( 'a' + i) + " count =" + total[i]);
}

The for loop loops until i=26 (where 26 is total.length) and then your if is executed, going over the bounds of the array. Remove the ; at the end of the for loop.