Can I use regular expression in contains method

Question

Here is my code

public class regMatch {

    public static void main(String... args)
    {
        String s = "1";
        System.out.println(s.contains("/[0-9]/"));
    }
}

Its printing false;

I want to use regular expression in contains method.

How can I use it.

I want to check whether is their any digit present in string or not — Pratik, Dec 26 '12 at 07:52
You're aware that the classes and methods are documented using javadoc, right? So why don't you checki it by yourself? http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#contains%28java.lang.CharSequence%29 — JB Nizet, Dec 26 '12 at 07:55
@Pratik: going to the javadoc and reading it is much faster than asking a question here. You didn't show any research effort, and that's why you deserve downvotes. — JB Nizet, Dec 26 '12 at 09:04

score 8 · Accepted Answer · edited Jun 20 '20 at 09:12

8

I want to use regular expression in contains method.

How can I use it

you can not use regex in contains method

edited Jun 20 '20 at 09:12

Community

1
1

answered Dec 26 '12 at 07:53

vishal_aim

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score 3 · Answer 2 · answered Dec 26 '12 at 07:53

You don't need (and shouldn't use) delimiters in a Java regex

And the contains() method doesn't support regexes. You need a regex object:

Pattern regex = Pattern.compile("[0-9]");
Matcher regexMatcher = regex.matcher(s);
System.out.println(regexMatcher.find());

score 1 · Answer 3 · answered Dec 26 '12 at 07:53

1

You can use the Pattern class to test for regex matches. However, if you are just testing for the presence of digits in the string, directly testing for this would be more efficient than using a regex.

answered Dec 26 '12 at 07:53

Michael Aaron Safyan

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score 1 · Answer 4 · answered Dec 26 '12 at 07:54

1

You can use matches() with the regex .*[0-9].* to find if there is any digit:

System.out.println(s.matches(".*[0-9].*"));

(or for multiline strings, use the regex (.|\\s)*[0-9](.|\\s)* instead)

An alternative - if you are eager to use contains() is iterate all chars from 0 to 9, and check for each if the string contains it:

    boolean flag = false;
    for (int i = 0; i < 10; i++) 
        flag |= s.contains("" + i);
     System.out.println(flag);

answered Dec 26 '12 at 07:54

amit

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This fails on multiline strings. – Tim Pietzcker Dec 26 '12 at 07:55
@TimPietzcker: Thanks for pointing that out. You can of course add `\\s` to the regex. See edit. – amit Dec 26 '12 at 07:58
2

Yikes. Better prepend `(?s)` to the regex. Or, even better, don't use `matches()` at all but `matcher.find()` which I proposed in my solution. – Tim Pietzcker Dec 26 '12 at 07:59
1

To add to Tim Pietzcker's comment, `(?s)` turns on DOTALL mode, which makes `.` matches anything. `.` by default does not match new line. – nhahtdh Dec 26 '12 at 08:02

Can I use regular expression in contains method

4 Answers4