comparing strings

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manzur - 07 Mar 2006 06:16 GMT

how do i know that the string which i have is in the my desired format
.

My format is z:y:x
where z,x,y are integers.

thnx in advance

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Bart Cremers - 07 Mar 2006 06:27 GMT

Use regular expressions.

Pattern patt = Pattern.compile("^\\d+:\\d+:\\d+$");
if (patt.matcher(input).matches()) {
// Yay!!!
} else {
// Boo
}

This code is not tested.

Regards,

Bart

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hiwa - 07 Mar 2006 06:29 GMT

if (myString.matches("^\\d:\\d:\\d$")){
...
}

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manzur - 07 Mar 2006 07:34 GMT

Greedy quantifiers
X? X, once or not at all
X* X, zero or more times
X+ X, one or more times
X{n} X, exactly n times
X{n,} X, at least n times
X{n,m} X, at least n but not more than m times

Reluctant quantifiers
X?? X, once or not at all
X*? X, zero or more times
X+? X, one or more times
X{n}? X, exactly n times
X{n,}? X, at least n times
X{n,m}? X, at least n but not more than m times

Possessive quantifiers
X?+ X, once or not at all
X*+ X, zero or more times
X++ X, one or more times
X{n}+ X, exactly n times
X{n,}+ X, at least n times
X{n,m}+ X, at least n but not more than m times

cn any one expalin me wht is the difference between the above three.
If some one can provide examples it would be great help
thnx in advance

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Roedy Green - 07 Mar 2006 07:43 GMT

>cn any one expalin me wht is the difference between the above three.

see http://mindprod.com/jgloss/regex.html

Sometime words fail. You need to write yourself a little test program
and feed it strings and see what it does.

Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

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manzur - 07 Mar 2006 07:57 GMT

wht actually i want to know was :
In Greedy quantifiers the api says
X? X, once or not at all

In Reluctant quantifiers the api says

X?? X, once or not at all

I was not able to understand wht X means in the above two scenarious.

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Jussi Piitulainen - 07 Mar 2006 08:23 GMT

> wht actually i want to know was :
> In Greedy quantifiers the api says
[quoted text clipped - 5 lines]
>
> I was not able to understand wht X means in the above two scenarious.

It stands for a regular expression. You can instantiate those
documentation lines with any old expression you want, as long as its
bound tight enough with respect to the quantifier.

[^_^]? matches [^_^] once or not at all
(<maybe>)? matches <maybe> once or not at all

X? stands for both of these, and many more.

<maybe>? matches <maybe and then > once or not at all

Here X? stands for >?.

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hiwa - 07 Mar 2006 09:00 GMT

Good read for regex novice:
http://java.sun.com/docs/books/tutorial/extra/regex/index.html
Differences Among Greedy, Reluctant, and Possessive Quantifiers
http://java.sun.com/docs/books/tutorial/extra/regex/quant.html

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Roedy Green - 07 Mar 2006 17:05 GMT

>I was not able to understand wht X means in the above two scenarious.

Did you read the link I gave you?
Did you do write an experimenting regex class?

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Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

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comparing strings

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