java - Regular Expression check length

Question

I have been trying to make a regular expression for my mobile phones but I can't seem to get it to work:

Here are the conditions for my regular expression:

• must start with 09
• total length is 9

Here is my regular expression:

[0]{1}[9]{1}[0-9]{7}

Valid mobile number 091123456

Invalid mobile number 0991234567 || 09912345

Answer 1

Easiest way:

^09[0-9]{7}$

Explanation:

^09 => begins by 09

[0-9] => any character between 0 and 9

{7} exactly seven times

$ => Ends with the latest group ([0-9]{7})