java - make characters optional in regular expression

Question

I am trying to validate a (US) phone number with no extra characters in it. so the format is 1-555-555-5555 with no dashes, spaces, etc and the 1 is optional. However, my regular expression will ONLY except numbers with the leading 1 and says numbers without it are invalid. Here is what I am using where did I go wrong?

"^(1)\d{10}$"

Answer 1

Use:

"^1?\d{10}$"

The ? means "optional".