Why does this data YYYY-MM-DD regex fail in Java?
- by ProfessionalAmateur
Hello StackOverFlow, My first question and Im excited... I've lurked since go-live and love the site, however I apologize for any newbie errors, formatting, etc...
I'm attempting to validate the format of a string field that contains a date in Java. We will receive the date in a string, I will validate its format before parsing it into a real Date object. The format being passed in is in the YYYY-MM-DD format. However I'm stuck on one of my tests, if I pass in "1999-12-33" the test will fail (as it should with a day number 33) with this incomplete pattern:
((19|20)\\d{2})-([1-9]|0[1-9]|1[0-2])-([12][0-9]|3[01])
However as soon as I add the characters in bold below it passes the test (but should not)
((19|20)\\d{2})-([1-9]|0[1-9]|1[0-2])-(0[1-9]|[1-9]|[12][0-9]|3[01])
*additional note, I know I can change the 0[1-9]|[1-9] into 0?[1-9] but I wanted to break everything down to its most simple format to try and find why this isn't working.
Here is the scrap test I've put together to run through all the different date scenarios:
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class scrapTest {
public scrapTest() {
}
public static void main(String[] args) {
scrapTest a = new scrapTest();
boolean flag = a.verfiyDateFormat("1999-12-33");
}
private boolean verfiyDateFormat(String dateStr){
Pattern datePattern = Pattern.compile("((19|20)\\d{2})-([1-9]|0[1-9]|1[0-2])-(0[1-9]|[1-9]|[12][0-9]|3[01])");
Matcher dateMatcher = datePattern.matcher(dateStr);
if(!dateMatcher.find()){
System.out.println("Invalid date format!!! -> " + dateStr);
return false;
}
System.out.println("Valid date format.");
return true;
}
}
Ive been programming for ~10 years but extremely new to Java, so please feel free to explain anything as elementary as you see fit.
