Some useful regex

Hi friends,
Here is another useful post but after a long time. I am not getting time these days :( anyway.. here we go;

A lot of checking and validations can be easily performed by using regular expressions (I use it extensively and trust me they are very useful). Here I am posting some commonly required regex:

1. Regex for checking valid email id:

^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$

2. Regex for checking password policy

((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{6,20})
Here, we are checking that the password should contain atleast 1 digit, atleast 1 lower case char, atleast 1 uppercase char and atleast 1 special char from @,#,$ and %
3. Regex for valid IPv4 IP address
^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.
([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])$

Enjoy