Thread: java.lang.ArrayIndexOutOfBoundsException ???

hello, i'm rather new to java and this is an assignment for my programming class. i keep getting the error in the title- i did look up what it means, but honestly i'm still clueless on what to do. can someone please tell me what i'm doing wrong?
here's my code:

 import java.io.*;
import java.util.*;
public class occurance { 
    public static void main(String args[]) {
        Scanner TMKF = new Scanner(System.in);
        System.out.println ("Please input a sentence and a letter that you want a count of.");
        String sentance = TMKF.nextLine();
        String letter = TMKF.nextLine();
        int letterCount = 0;
        int n=-1;
        String[] arr = new String[sentance.length()];
        for( int i = 0; i < sentance.length(); i++){
            arr[i] = String.valueOf(sentance.charAt(i) );
        }
        do {
            n++;
            if(arr[n]==letter) {
                letterCount++;
            }
        } while (n < arr.length); 
        System.out.println (sentance + " has " + letterCount + " occurance(s) of the letter " + letter);
    }
}

java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1
at occurance.main(occurance.java:17)

^the full error message

thank you in advance.

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