Regex working in regexpal but not in Java

Question

I have a simple regex which searches a sentence to see if it contains the word of|for|in|at and here is my regex that is almost working in regexpal:

[^A-Za-z]of|for|in|at[^A-Za-z]

I run it on following setences:

show me the weather of seattle
show me the weather in seattle
show me the weather for seattle
show me the weather at seattle

and here are results:

enter image description here

When I use it in my Java code it doesnt works at all. In regexpal too is shows space with for and at which I defined at start and end. Can someone please tell what is wrong with my regex and how to search for one of many words in a sentence

I always get else condition in my java which means it is not matching regex. Here is my java code:

public class Regex 
{
public static void main(String[] args)
{
    String str = "show me the weather in seattle";

    if(str.matches("[^A-Za-z]of|for|in|at[^A-Za-z]")){
        System.out.println("Yayyy!!");
    }
    else{
        System.out.println("OMG now what to do");
    }       
}
}

matches checks the string is completely. It is not looking for a match. try add .* at start and end regexp — turbanoff
– turbanoff, Commented Apr 17, 2012 at 3:22
also, your "space" is only in front of "of" and after "at". use [^A-Za-z](of|for|in|at)[^A-Za-z] or, better, \\W(of|for|in|at)\\W — andrew cooke
– andrew cooke, Commented Apr 17, 2012 at 3:24
@turbanoff I tried .* but problem is it even matches "show me the weather seattle" when I remove "at" because at is present in weather and seattle. I need independent occurance of any word hence I used [^A-Za-z] — Yogesh
– Yogesh, Commented Apr 17, 2012 at 3:31
@andrewcooke Your code works perfectly in regexcode but not in java. Do I need to append something in str.matches(regex) to make it work for java — Yogesh
– Yogesh, Commented Apr 17, 2012 at 3:37

prajeesh kumar · Accepted Answer · 2012-04-17 04:35:09Z

1

Doesn't this work .*[^A-Za-z](of|for|in|at)[^A-Za-z].* ?. Ofcourse you will need to do extra to check for the boundary cases where of|for|in|at is either the start or the end of the word.

answered Apr 17, 2012 at 4:35

prajeesh kumar

1,9661 gold badge17 silver badges17 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Yogesh Over a year ago

Thanks. It works. In my statements those words will appear between the statements only. Regards

Eli Sand Over a year ago

You shouldn't need the .* at all. The regular expression is being bound to a non letter before and after any one of the words in the set; adding .* is completely unnecessary and pointless.

prajeesh kumar Over a year ago

@EliSand You didn't understand that the mathes method checks whether the full string is matched by the regex right ? It is like that, so your assumption works only when there is no other "letter" in the string before and after the match. So here it works like - May be some characters, whatever,then a non letter,then what I am looking for,then a non letter,then may be some more characters,whatever :-)

prajeesh kumar Over a year ago

@EliSand And also before saying un-necessary and pointless you should come with a different working answer, do you have any ?

Eli Sand Over a year ago

I retract my comment - I assumed that no-one would ever create a function that implicitly implies ^ and $ on a regex. It saves two characters and prevents functionality... alas I didn't write Java. My apologies on the confusion.

Eli Sand · Accepted Answer · 2012-04-17 03:24:03Z

1

[^A-Za-z](?:of|for|in|at)[^A-Za-z]

You want to group the "or" matches, otherwise it thinks you mean:

[^A-Za-z]of  OR  for  OR  in  OR  at[^A-Za-z]

which is very likely not what you want.

answered Apr 17, 2012 at 3:24

Eli Sand

1,0327 silver badges11 bronze badges

3 Comments

Eli Sand Over a year ago

Pro-tip: the ?: part inside the () makes the match just a group but not usable as a match entity or whatever the technical mumbo jumbo description is.

Yogesh Over a year ago

It works regex pal but not in java. In Java my code again goes to else case, do I need to append something to it to call in str.matches(). And yes I want occurence of 1 of or for or in or at. I want it to be able to see whether user has any of [of|for|in|at] in his statements

Eli Sand Over a year ago

If I'm understanding what you're actually trying to achieve with your regular expression, you should use \b(of|for|in|at)\b. Also, does .matches() return true/false or some condition that can be tested as such?

Collectives™ on Stack Overflow

Regex working in regexpal but not in Java

2 Answers 2

5 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related