Why does this java regular expression not work?

Why does this Pattern not match the port in my URL?

public class PatternTest {
    private Pattern PORT_STRING_PATTERN = Pattern.compile(":\\d+/");

    private boolean hasPort(String url) {
        return PORT_STRING_PATTERN.matcher(url).matches();
    }

    @Test
    public void testUrlHasPort() {
        assertTrue("does not have port", hasPort("http://www.google.com:80/"));
    }
}

If I change the pattern to Pattern.compile("^.+:\\d+/") it does match. Why do I need the ^.+ ?

Jon Skeet
people
quotationmark

The problem is that you're using Matcher.matches(), which is documented as:

Attempts to match the entire region against the pattern.

You don't want to match the entire region - you just want to find a match within the region.

I think you probably want to be calling find() instead:

Attempts to find the next subsequence of the input sequence that matches the pattern.

This method starts at the beginning of this matcher's region, or, if a previous invocation of the method was successful and the matcher has not since been reset, at the first character not matched by the previous match.

people

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