Question

Is there any way I can format a string into a specific pattern using regex or is stringbuilder + substring a faster approach?

For example, say a phone number –> 1234567890 as input

And get output as –> [phone]

I saw it is possible on this article : https://web.archive.org/web/20211020111604/https://www.4guysfromrolla.com/webtech/031302-1.shtml but the given explanation is in ASP. How do I do it in Java ???

Answer 1

One goes for RE when same can not be done using substring or is more difficult to do so.

In your case better to just use StringBuilder and insert()

Assuming phone number length validation is in place (=10 chars)

        String phoneNumber = "1234567890";
        StringBuilder sb = new StringBuilder(phoneNumber)
                                .insert(0,"(")
                                .insert(4,")")
                                .insert(8,"-");
        String output = sb.toString();
        System.out.println(output);          

Output

[phone]