using regex in java for validate email

Question

I am trying to validate a certain subset of the e-mail format with regular expressions, but what I've tried so far doesn't quite work. This is my regex (Java):

boolean x = l.matches(
    "^[_A-Za-z0-9-\\\\+]+(\\\\.[_A-Za-z0-9-]+)*@\"\n" +"+ \"[A-Za-z0-9-]+(\\\\.[A-Za-z0-9]+)*(\\\\.[A-Za-z]{2,})$"
);

Thse are the conditions that the string has to match:

• Mail domain is from the list:

  • www.fightclub.uk
  • www.fightclub.lk
  • www.fightclub.sa
  • www.fightclub.cc
  • www.fightclub.jp
  • www.fightclub.se
  • www.fightclub.xy
  • www.fightclub.gi
  • www.fightclub.rl
  • www.fightclub.ss

• username has 3 to 6 characters(only lowercase English letters and numbers)

examples:

sonia6@fightclub.com is valid

am@fightclub2.lk is invalid

Answer 1

You can use:

^[a-z0-9]{3,6}@fightclub\.(?:uk|lk|sa|cc|jp|se|xy|gi|rl|ss)$

1. ^ indicates start of string
2. [a-z0-9]{3,6} lowercase letters or number with length 3-6 characters
3. followed by @fightclub
4. followed by a period \.
5. followed by a list of domains (?: indicate that it's a non-capturing group. All your domain extensions are listed here.
6. $ indicates end of string

DEMO: https://regex101.com/r/rYYXYA/1