Java Regular Expression

Java has comprehensive support for Regular Expression functionality through the java.util.regex package. The regular expression language is easy to learn but hard to master, the better way to learn it is through examples. In theoretical, regular expression can match almost any stuff you want, the only limitation is in your imagination.
Happy learning Java Regular Expression :)

ජාවා java.util.regex පැකේජය හරහා Regular Expression ක්රියාකාරීත්වය සඳහා පුළුල් සහයෝගය හිමිවේ.

Username regular expression example in Java.
^[a-z0-9_-]{3,15}$

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

Hex color code regular expression example in Java.
^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$

E-mail address regular expression example in Java .
^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@
[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$

Image file extension regular expression example in Java.
([^\s]+(\.(?i)(jpg|png|gif|bmp))$)

IP Address regular expression example in Java.
^([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])$

Time in 12 Hours format regular expression example in Java.
(1[012]|[1-9]):[0-5][0-9](\\s)?(?i)(am|pm)

Time in 24 Hours format regular expression example in Java.
([01]?[0-9]|2[0-3]):[0-5][0-9]

Date regular expression example in Java.
(0?[1-9]|[12][0-9]|3[01])/(0?[1-9]|1[012])/((19|20)\\d\\d)

HTML tag regular expression example in Java.
<("[^"]*"|'[^']*'|[^'">])*>

HTML links regular expression example in Java.
(?i)<a([^>]+)>(.+?)</a>
\s*(?i)href\s*=\s*(\"([^"]*\")|'[^']*'|([^'">\s]+));

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Java Regular Expression