java - What will be the output of String.substring(String.length)?

Question

public class Str {

    public static void main(String[] args) {

        String str = "abcde";
        String s = str.substring(str.length());
        System.out.println(s);
    }

}

The index of character 'e' is 4, but I am trying to get the whole string of length 5. If I execute the code above, why it is not throwing the IndexOutOfBoundsException?

Answer 1

The JavaDoc for String.substring() states:

[throws] IndexOutOfBoundsException - if beginIndex is negative or larger than the length of this String object.

Since your beginIndex is equal to the length of the string it is a valid value and substring() returns an empty string.