String matches() method

Thread view:

Sharp - 02 May 2005 09:15 GMT

Hi

I have a string, for example:

String str = "aaab";

I would like to use the matches() method of the String class to test the
string's first 3 characters are identical.
I would like to do this in a general way by using regular expressions.

Tried (but doesn't work):

if (str.matches("xxx[a-zA-Z]"))
return true;

According to the regular expression, x is suppose to be a character.
Not sure, why this is not working, or if it's even possible to do it using
the matches method.
Any help appreciated.

Cheers
Sharp

Reply to this Message

Daniel Sjöblom - 02 May 2005 11:12 GMT

> I would like to use the matches() method of the String class to test the
> string's first 3 characters are identical.

> Tried (but doesn't work):
>
> if (str.matches("xxx[a-zA-Z]"))
> return true;
>
> According to the regular expression, x is suppose to be a character.

Here, x is a character, that is 'x'. To achieve what you want you would
need something like "((.)\\2\\2).*". But using regexes is not the right
answer to this problem. It is better to write a method that just checks
that the first three characters are the same. It's just a couple of
lines of code, probably faster than using a regex too.

Signature

Daniel Sjöblom
Remove _NOSPAM to reply by mail

Reply to this Message

Sharp - 02 May 2005 12:16 GMT

> > I would like to use the matches() method of the String class to test the
> > string's first 3 characters are identical.
[quoted text clipped - 11 lines]
> that the first three characters are the same. It's just a couple of
> lines of code, probably faster than using a regex too.

Thanks for your help.
Your suggested regular expression works, but I dont fully understand it.
I assume that '\\2' means same as the previous character, which is '.'
Not sure what the '*' means.
Could you shed some light on the whole thing?

Cheers
Sharp

Reply to this Message

hiwa - 02 May 2005 12:40 GMT

>>
>>
[quoted text clipped - 26 lines]
>Sharp
>

\\2 is \2 which means capturing group 2.
* means zero or more.
Read the javadoc for Pattern class.

Reply to this Message

Sharp - 02 May 2005 12:52 GMT

> >>>I would like to use the matches() method of the String class to test the
> >>>string's first 3 characters are identical.
[quoted text clipped - 24 lines]
> * means zero or more.
> Read the javadoc for Pattern class.

Thanks!

Cheers
Sharp

Reply to this Message

Christian Gudrian - 02 May 2005 12:43 GMT

Am Mon, 02 May 2005 11:16:57 GMT schrieb Sharp:

> Could you shed some light on the whole thing?

http://www.amk.ca/python/howto/regex/

Christian

Reply to this Message

String matches() method

Free Magazines