Java Regex Date Validation Example

Java Regex Date Validation Example

Date Regex Pattern

 

(0?[1-9]|[12][0-9]|3[01])/(0?[1-9]|1[012])/((19|20)\\d\\d)

 

(	start of group =1
0?[1-9]	01-09 or 1-9
|	..or
[12][0-9]	10-19 or 20-29
|	..or
3[01]	30, 31
)	end of group =1
/	follow by a "/"
(	start of group =2
0?[1-9]	01-09 or 1-9
|	..or
1[012]	10,11,12
)	end of group =2
/	follow by a "/"
(	start of group =3
(19|20)\\d\\d	19[0-9][0-9] or 20[0-9][0-9]
)	end of group =3

 

Example

package mycollectiontest;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexExample {
   private Pattern pattern;
   private Matcher matcher;

   private static final String DATE_PATTERN = "(0?[1-9]|[12][0-9]|3[01])/(0?[1-9]|1[012])/((19|20)\\d\\d)";

   public RegexExample() {
      pattern = Pattern.compile(DATE_PATTERN);
      String input = "1/1/2012";
      System.out.println("input : " + input + " " + validate(input));

      String input1 = "32/13/2010";
      System.out.println("input : " + input1 + " " + validate(input1));
   }

   public boolean validate(final String date) {
      matcher = pattern.matcher(date);

      if (matcher.matches()) {

         matcher.reset();

         if (matcher.find()) {
            String day = matcher.group(1);
            String month = matcher.group(2);
            int year = Integer.parseInt(matcher.group(3));
            if (day.equals("31") && (month.equals("4") || month.equals("6") || month.equals("9") || month.equals("11")
                  || month.equals("04") || month.equals("06") || month.equals("09"))) {
               return false; // only 1,3,5,7,8,10,12 has 31 days
            } else if (month.equals("2") || month.equals("02")) {
               // leap year
               if (year % 4 == 0) {
                  if (day.equals("30") || day.equals("31")) {
                     return false;
                  } else {
                     return true;
                  }
               } else {
                  if (day.equals("29") || day.equals("30") || day.equals("31")) {
                     return false;
                  } else {
                     return true;
                  }
               }
            } else {
               return true;
            }
         } else {
            return false;
         }
      } else {
         return false;
      }
   }

   public static void main(String[] args) {
      new RegexExample();
   }
}

Output

input :  1/1/2012   true
input :  32/13/2010   false