Substring in Java - length up to a value

Question

I'm trying to make a substring which lets me have up to 6 letters of a surname, however what I have here seems to throw an error when it finds a surname of less than 6 letters, I have been looking for hours for a solution with no sucess :/

id = firstName.substring (0,1).toLowerCase() + secondName.substring (0,6).toLowerCase();
System.out.print ("Here is your ID number: " + id);

It's the .substring(0,6). I need it to be up to 6 letters not exactly 6.

The error:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 6
    at java.lang.String.substring(Unknown Source)
    at Test.main(Test.java:27)

Answer 1

I prefer

secondName.length > 6 ? secondName.substring(0, 6) : secondName

Answer 2

Use

secondName.substring (0, Math.min(6, secondName.length()))