Checking a number with regular expressions in Java

Question

I have a number "8756342536". I want to check whether the number starts with "8", contains 10 digits all of it is numeric, using regular expression.

What pattern would I need for this scenario in Java? Thanks in advance.

Answer 1

Use String's matches(...) method:

boolean b = "8756342536".matches("8\\d{9}");

Answer 2

Use this expression:

^8\d{9}$

meaning an 8 followed by exactly 9 digits. So for example:

String number = ...
if (number.matches("^8\\d{9}$")) {
  // it's a number
}