title: How do I exclude certain characters from pattern matching in regex?
body: <p>I'm trying to implement my own version of atoi and so I want to check if my string contains non-numeric characters and handle the error, but I also also want the search pattern to exclude the + and - symbols (i.e + and - at the start of the string only are valid symbols). I currently have <code>word.matches("^[+=][a-zA-Z]+")</code>, but am not sure how to change it accordingly to fit my needs.
  Ex: 20e48 is invalid, 204-8 is invalid, +2048 is valid and so is -2048</p>