Java pattern: regexp - Allow few special character in between character-CodePudding

I am trying to allow some character through regular expression. I want to allow word with special character like ( - _ & spaces) in between the character. Also i am allowing number in a word along with letter.

Valid:

a_B
a_b
a b
a B
a_btest_psom
a-B
a43 b
a43_c

Invalid:

a_
_a
a-
a_b_
a_B_
a_b-
a_btest_psom_ (at end only special character)
43 b (starting with number)
43_c (starting with number)
434343 (only numbers)

Code:

import javax.validation.constraints.Pattern;

public static final String PATTERN="^[a-zA-Z0-9 _-]*$"; 
@Pattern(regexp = PATTERN)
private String companyName;

Using above code, I am not able to achieve as per my expectation. Can you help me on this?

CodePudding user response：

You can use

^[a-zA-Z][a-zA-Z0-9]*(?:[ _-][a-zA-Z0-9] )*$

See the regex demo

Details:

^ - start of string
[a-zA-Z][a-zA-Z0-9]* - a letter and then zero or more letters or digits
(?:[ _-][a-zA-Z0-9] )* - zero or more sequences of a space/_/- and then one or more letters or digits
$ - end of string.

CodePudding user response：

Please try this regex.

^[a-zA-Z][A-Za-z0-9 ()/]*$

You can add whatever special character you want in your regex. Modify it as per your requirement.

CodePudding user response：

Just adding in this in the begining [a-zA-Z] and at the end [a-zA-Z0-9] should work.

^[a-zA-Z][a-zA-Z0-9 _-]*[a-zA-Z0-9]$ that means that first char should be a character and the last char should be a character or a number.

Use this: ^[a-zA-Z][a-zA-Z0-9 _-]*[a-zA-Z]$ if it doesnt have to finish with a number.