Archives: Regular Expressions

Java – Date Validation with Regular Expression

Date Format (dd/mm/yyyy) Regular Expression Pattern

(0?[1-9]|[12][0-9]|3[01])/(0?[1-9]|1[012])/((19|20)\\d\\d)

The above regular expression is used to validate the date format in “dd/mm/yyyy”, you can easy customize to suit your need. However, it’s a bit hard to validate the leap year, 30 or 31 days of a month, we may need basic logic as below.


Java – Password Validation with Regular Expression

Password Regular Expression Pattern:

((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{6,20})

Whole combination is means, 6 to 20 characters string with at least one digit, one upper case letter, one lower case letter and one special symbol (“@#$%”). This regular expression pattern is very useful to implement a strong and complex password.


Java – Username Validation with Regular Expression

Username Regular Expression Pattern:   ^[a-z0-9_-]{3,15}$

Description:
^     # Start of the line
[a-z0-9_-]  # Match characters and symbols in the list, a-z, 0-9, underscore, hyphen
{3,15}      # Length at least 3 characters and maximum length of 15
$       # End of the line

Example: