Regular expression String for URL in JAVA

Question

I would like to check URL Validation in JAVA with regular-expression. I found this comment and I tried to use it in my code as follow...

private static final String PATTERN_URL = "/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[-;:&=\+\$,\w]+@)?[A-Za-z0-9.-]+(:[0-9]+)?|(?:ww‌w.|[-;:&=\+\$,\w]+@)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%@.\w_]*)#?‌(?:[\w]*))?)/";

.....
if (!urlString.matches(PATTERN_URL)) {
  System.err.println("Invalid URL");
  return false;
}

But I got compile time exception for writing my PATTERN_URL variable. I have no idea how to format it and I am worried about will it become invalid regex if I have modified. Can anyone fix it for me without losing original ? Thanks for your helps.

aliteralmind · Accepted Answer · 2014-02-26 04:28:21Z

4

Your regex looks fine. You just need to format it for a Java string, by escaping all the escape-slashes:

\ --> \\

Resulting in this:

"/((([A-Za-z]{3,9}:(?:\\/\\/)?)(?:[-;:&=\\+\\$,\\w]+@)?[A-Za-z0-9.-]+(:[0-9]+)?|(?:ww‌w.|[-;:&=\\+\\$,\\w]+@)[A-Za-z0-9.-]+)((?:\\/[\\+~%\\/.\\w-_]*)?\\??(?:[-\\+=&;%@.\\w_]*)#?‌(?:[\\w]*))?)/"

After Java interprets this string into a java.util.regex.Pattern, it will strip out those extra escape-slashes and become exactly the regex you want. You can prove this by printing it:

System.out.println(Pattern.compile(PATTERN_URL));

edited Feb 26, 2014 at 4:28

answered Feb 26, 2014 at 4:21

aliteralmind

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5 Comments

Cataclysm Over a year ago

yes , thanks for great help. What is different between String.matches("regex")and java.util.Pattern.compile('regex') ?

aliteralmind Over a year ago

Not much, unless you need to do it over and over, then you'll want to go with the Pattern object, which avoids re-compiling the Pattern every iteration (this is what String.matches(s) does behind the scenes). See the "typical invocation" at the top of this page: docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

Cataclysm Over a year ago

pls don't be mind , pls teach me what would be more preferable because my another validation methods also used with String.matches("regex") unless I have know exatly about it. Thanks.

aliteralmind Over a year ago

If you're doing it over and over again, use Pattern and Matcher. If you're only doing it once per execution, for example, then stick with String.matches(s).

Cataclysm Over a year ago

Now compile time error has fixed but validation result does not produce as expected.. what am I wrong ? It does no return true even mail.google.com. any suggestions ?

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