CODEWITHSUNDEEP
javaregex
TheLostMind
TheLostMind

Reputation: 36304

Why is regex Pattern matching "|" in the below displayed code?

Ok. I know that i am missing something. I am just not able to find out what I am missing. The below mentioned pattern matches "|" and i don't know why. Can someone please explain. thanks. I want to match a single character. The character set is {,},[,],|,? etc.

public static void main(String[] args) {
    String str = "";
    if (str.matches("[\"|`|+|,|;|<|>|?|\\[|\\]|{|}|']"))
        System.out.println("matches");

}

Upvotes: 0

Views: 72

Answers (4)

reinierpost
reinierpost

Reputation: 8591

You are mixing up two different ways of specifying alternatives:

Pick one.

Upvotes: 0

Krishna M
Krishna M

Reputation: 1195

In short, You have given | in the [ ] brackets.

Any character within square brackets[ ] will be matched.

Remove all the | inside the braces.

Upvotes: 0

Dropout
Dropout

Reputation: 13866

You don't need to use the | sign in the regex, because you're using an array of characters to match to. Basically if you want to match something to a,b,c or d, which means that the string can contain any of those letters you can simply do

String pattern = "[abcd]*"; // * means they can be repeated, for example "aabdcb"
str.matches(pattern);

No need to use the pipe. On the other hand if you want to strictly say that a string is either a or b you can use a pattern like

pattern = "(a)|(b)"; // matches either "a" or "b"

Hope this clears up things a bit for you.

You might want to check out this page to learn more about using pipe in regexes.

Upvotes: 2

Sean Owen
Sean Owen

Reputation: 66886

You are using [] to start and end the expression, when it looks like you are using syntax that goes with (). The square braces let you list a bunch of characters that match, and | is in your list many times. Parentheses set up a grouping inside which you can use | to mean "or".

I think the solution for you is to remove those |. You don't separate characters inside square braces with anything, you just list them all.

Upvotes: 3

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