it compiles but gives me an exception

the program is suppose to intake sentence and return the number of uppercase letter, lower case , and digits. it compiles asks for input and returns:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 9
    at java.lang.String.charAt(Unknown Source)
    at projects.projectzero.check(projectzero.java:16)
    at projects.projectzero.main(projectzero.java:10)

---

package projects;

import javax.swing.JOptionPane;

public class projectzero {
    public static void main(String args[]) {
        String sentence = "", addToSentence = "";
        while (!addToSentence.equalsIgnoreCase("stop")) {
            addToSentence = JOptionPane.showInputDialog("input words or enter  stop to end program");
            sentence += addToSentence;
        }
        check(sentence);
    }

    public static void check(String input) {
        int upperCase = 0, lowerCase = 0, numbers = 0;
        for (int i = 0; i <= input.length(); i++) {
            char c = input.charAt(i);
            if (Character.isUpperCase(c))
                upperCase++;
            else if (Character.isLowerCase(c))
                lowerCase++;
            else if (Character.isDigit(c)) numbers++;
        }
        System.out.println("the number of uppercase: " + upperCase + " the number of lower case : " + lowerCase + "the number of digits is: "
                + numbers);
    }
}

---

appreciate the help :)