Java正则表达式不起作用

Question

I am trying to match input data from the user and search if there is a match of this input. for example if the user type : A*B*C* i want to search all word which start with A and contains B and B i tried this code and it;s not working:(get output false)

public static void main(String[] args)
    {

        String envVarRegExp = "^A[^\r\n]B[^\r\n]C[^\r\n]";
        Pattern pattern  = Pattern.compile(envVarRegExp);
        Matcher matcher = pattern.matcher("AmBmkdCkk");
        System.out.println(matcher.find());

    }

Thanks.

Answer 1

You don't really need Regex here. Simple String class methods will work: -

String str = "AfasdBasdfCa";

if (str.startsWith("A") && str.contains("B") && str.contains("C")) {
    System.out.println("true");
}

Note that this will not ensure that your B and C are in specific order, which I assume you don't need as you have not mentioned anything about that.

If you want them to be in some order (like B comes before C then use this Regex: -

if (str.matches("^A.*B.*C.*$")) {
    System.out.println("true");
}

Note that, . will match any character except newline . So, you can use it instead of [^\\r\\n] , its more clear. And you need to use the quantifier * because you need to match any repetition of the characters before B or C is found.

Also, String.matches matches the complete string, and hence the anchors at the ends.

Answer 2

您需要在字符类中添加量词。

String envVarRegExp = "^A[^\r\n]*B[^\r\n]*C[^\r\n]*$";

Answer 3

I thing you should use * modifier in your regex like this (for 0 or more matches between A & B and then between B & C):

String envVarRegExp = "^A[^\r\n]*B[^\r\n]*C";

EDIT: It appears that you're working off the input coming from your user where user can use asterisk * in inputs. If that is the case consider this:

String envVarRegExp = userInput.replace("*", ".*?");

Where userInput is String like this:

String userInput = "a*b*c*d*e";