java string regex

could someone help me开发者_运维技巧 out with a piece of regex please? I want to stop the user entering any charachter other than a-z or a hyphen -

Hope someone can help me.

Thanks

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You can use the regex: ^[a-z-]+$

• ^ : Start anchor
• $ : End anchor
• [..] : Char class
• a-z : any lowercase alphabet
• - : a literal hyphen. Hyphen is usually a meta char inside char class but if its present as the first or last char of the char class it is treated literally.
• + : Quantifier for one or more

If you want to allow empty string you can replace + with *

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If the string doesn't match ^[a-z-]*$, then a disallowed character was entered. This pattern is anchored so that the entire string is considered, and uses a repeated character class (the star specifies zero or more matches, so an empty string will be accepted) to ensure only allowed characters are used.

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If you allow uppercase use this:

^[A-Za-z-]+?$

otherwise:

^[a-z-]+?$

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If a string matches this regex ^[a-z\-]*$ then its fine.