Java regex to check if a pattern exists

Question

I am trying to find whether a pattern exists in a string.

Pattern I want to check is:

String starting with space or "#",
then with specific string "value1" followed by space or tab,
then "value2" and again space or tab,
ends with "value3".

Here a sample string to check:

String str = "#  value1   values2 value3";

I tried the following regular expression, but it did't work:

str.matches("^\\s+#\\s+value1\\s+value2\\s+value3");

The above pattern always returns me false. Please help with regular expression. Any help will be really appreciated.

Do you want to match a single space at the start or double space? — Rohit Jain
– Rohit Jain, Commented Oct 25, 2012 at 16:12
You said you want to match whether the string starts with a # or a space. But the string you posted starts with both: - # value1 values2 value3. It has both a # followed by a space. — Rohit Jain
– Rohit Jain, Commented Oct 25, 2012 at 16:17
Did you realize that String str = "# value1 values2 value3" got an S in values2 and that's because your regex is not working? (apart of \\s#, use @RohitJain one) — Javier Diaz
– Javier Diaz, Commented Oct 25, 2012 at 17:04

Rohit Jain · Accepted Answer · 2012-10-25 16:42:27Z

4

Try this: -

str.matches("^[ #]value1\\s+value2\\s+value3$");

[ #] - matches a space or #

\\s+ - matches 1 or more spaces. So, it would match a space or tab

NOTE: - You have values2 instead of value2 in your string.

Also, your example string you posted, has both a space and a # at the starting. But you said the string starts with a space or a #. So, it will match your string, if you remove that space after the first #, or your # before your space, which is according to what you wrote.

If you want to match a space and a # at the starting of your string, as in your current String you posted. You need to use this regex: -

str.matches("^[ #]\\svalue1\\s+value2\\s+value3$");

edited Oct 25, 2012 at 16:42

answered Oct 25, 2012 at 16:06

Rohit Jain

214k45 gold badges419 silver badges534 bronze badges

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

9 Comments

Sam I am says Reinstate Monica Over a year ago

u think the asker needs to match " value1 values2 value3", because your regex will not match that.

Rohit Jain Over a year ago

@JanDvorak Ah sorry. I got confused. Actually OP wrote something else, and his example string says something else.

Sam I am says Reinstate Monica Over a year ago

@RohitJain Did you know that you can click on you score to actually see whether or not any downvotes have been made on your answer. I would assume not since your answer has recieved none, yet you seem to assume that i downvoted

Rohit Jain Over a year ago

@JanDvorak. OP has this string: - # value1 values2 value3 and said he want to start with a space or #, so I thought may be he wants a space and # or 2 spaces.

John Dvorak Over a year ago

Perhaps he means # or space or both

|

Sam I am says Reinstate Monica · Accepted Answer · 2012-10-25 16:32:12Z

1

Well, I can tell you right now that that regex WILL fail for that input because it requires whitespace before the #

try

str.matches("^#?\\s+value1\\s+value2\\s+value3$");

that regex should match "# value1 value2 value3" or " value1 value2 value3" with variable amounts of whitespace

edited Oct 25, 2012 at 16:32

answered Oct 25, 2012 at 16:07

Sam I am says Reinstate Monica

31.3k12 gold badges75 silver badges101 bronze badges

8 Comments

John Dvorak Over a year ago

requirement: 'starting with space or "#"'

Sam I am says Reinstate Monica Over a year ago

@JanDvorak it does start with a space or #

Sam I am says Reinstate Monica Over a year ago

@JanDvorak does that \\s+ after the #? not require a space in order to be matched?

John Dvorak Over a year ago

\\s+ always requires a space in order to match.

Sam I am says Reinstate Monica Over a year ago

@JanDvorakn then the regex I posted will only match strings that start with a # or a space won't it.

|

RamValli · Accepted Answer · 2015-02-13 09:38:12Z

0

Try this regex (\s+|\s?#\s?).*value1.*(\s+|\t).*value2.*(\s+|\t).*value3.* It works even if you have whitespaces anywhere.

answered Feb 13, 2015 at 9:38

RamValli

4,4952 gold badges37 silver badges47 bronze badges

Collectives™ on Stack Overflow

Java regex to check if a pattern exists

3 Answers 3

9 Comments

8 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

9 Comments

8 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related