Accepting date strings (MM-dd-yyyy format) using Java regex?

The following is the regular expression to match the date in the dd-MM-yyyy format.

^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$

To match a date in a string in that format.

• Compile the above expression of the compile() method of the Pattern class.

• Get the Matcher object bypassing the required input string as a parameter to the matcher() method of the Pattern class.

• The matches() method of the Matcher class returns true if a match occurs else it returns false. Therefore, invoke this method to validate the data.

Example 1

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MatchingDate {
   public static void main(String[] args) {
      String date = "01/12/2019";
      String regex = "^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$";
      //Creating a pattern object
      Pattern pattern = Pattern.compile(regex);
      //Matching the compiled pattern in the String
      Matcher matcher = pattern.matcher(date);
      boolean bool = matcher.matches();
      if(bool) {
         System.out.println("Date is valid");
      } else {
         System.out.println("Date is not valid");
      }
   }
}

Output

Date is valid

The matches() method of the String class accepts a regular expression and matches the current string with it and returns true in case of a match and else returns false. Therefore, to verify if the given date (in string format) is in the required format −

• Get the date string.
• Invoke the matches() method on it by passing the above regular expression as a parameter to it.

Example 2

import java.util.Scanner;
public class Just {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter your name: ");
      String name = sc.nextLine();
      System.out.println("Enter your Date of birth: ");
      String dob = sc.nextLine();
      //Regular expression to accept date in MM-DD-YYY format
      String regex = "^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$";
      boolean result = dob.matches(regex);
      if(result) {
         System.out.println("Given date of birth is valid");
      } else {
         System.out.println("Given date of birth is not valid");
      }
   }
}

Output 1

Enter your name:
Janaki
Enter your Date of birth:
26/09/1989
Given date of birth is not valid

Output 2

Enter your name:
Janaki
Enter your Date of birth:
09/26/1989
Given date of birth is valid