what is the meaning of arguments in substring method of String class

Question

class Test {

    public static void main(String[] args) {
       String str="Hello world";
        System.out.println(str.substring(0, 4));
    }
}

why the output is not Hello ? if the substring method's arguments indicate the starting and ending point respectively. And here strating from 0 index why does it end before index 4.i mean why been here the index 4 character not printed

Answer 1

str.substring(0, 4) retrieve part of the given str from index 0 inclusive to index 4 exclusive. Result is Hell .

See Java doc for String class: public CharSequence subSequence(int beginIndex, int endIndex)