Java BufferedReader error : How can I fix the following error:
`   Exception in thread "main" java.lang.StringIndexOutOfBoundsException: begin 3, end 4, length 3
    at java.base/java.lang.String.checkBoundsBeginEnd(String.java:3116)
    at java.base/java.lang.String.substring(String.java:1885)
    at ReadZILLA.main(Main.java:26)`
This is the code:

    import java.io.*;
    import java.text.*;
    class ReadZILLA {

    public static void main(String[] args) throws IOException {
        int vowel = 0;
        int words = 0;
        int line = 10;
        int line_no = 11-line;
        int n = 1;
        String a = "a";
        String e = "e";
        String i = "i";
        String o = "o";
        String u = "u";
        String A = "A";
        String E = "E";
        String I = "I";
        String O = "O";
        String U = "U";
        String space = " ";
        BufferedReader in_text = new BufferedReader(new InputStreamReader(System.in));
        String text = in_text.readLine();

        while(line > 1){
            String char_def = text.substring(n-1,n);
            System.out.println(char_def);
        
            if (char_def == a || char_def == e || char_def == i || char_def == o || char_def == u || char_def == A || char_def == E || char_def == I|| char_def == O || char_def == U){
                vowel = vowel + 1;
            } else if (char_def == space){
                words = words +1;
            } else if (char_def == "\n"){
                System.out.println ("Numbers of vowels: " + vowel + "in line " + line_no);
                vowel = 0;
                line = line-1;

            }

            n = n +1;

        }

        int words_avg = words/10;
        System.out.println("Number of words: " + words);
        System.out.println("Average number of words: " + words_avg);

    }


The program is called ReadZILLA and it's supposed to output the numbers of vowels, words and average words in a line from the input.
E.G input: tHe DoG is BrOWN /n thE cat IS rED
output: vowels: 8, words: 8, average words per line: 4

