Question

I’m trying to build a Java regex that supports date times (where the time component is military time):

MM/dd/YYYY HH:mm:ss

@Test
public void testRegexPattern() {
    String regex = "([0-9]{2})/([0-9]{2})/([0-9]{4}\\s^([01]\\d|2[0-3]):?([0-5]\\d):?([0-5]\\d)$)";

    String supposedDateTime = "12/31/1969 19:00:00";

    Assert.assertTrue(supposedDateTime.matches(regex));
}

This test is failing because the supposedDateTime doesn’t match the regex. Can any regex maestros out there spot why? Thanks in advance.

Answer 1

Why are you having caret(^) in the middle after \\s? Remove it. That is what creating the problem. Also, with String#matches method, you don’t even need to use anchors.

So, you can use this regex:

"([0-9]{2})/([0-9]{2})/([0-9]{4}\\s([01]\\d|2[0-3]):?([0-5]\\d):?([0-5]\\d))"

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Having talked about the actual issue in regex, you should really not test dates with regex. Rather use SimpleDateFormat with appropriate pattern to parse the date string.