Matcher pattern() method in Java with Examples

JavaObject Oriented ProgrammingProgramming

The java.util.regex.Matcher class represents an engine that performs various match operations. There is no constructor for this class, you can create/obtain an object of this class using the matches() method of the class java.util.regex.Pattern.

The pattern() method of this (Matcher) class fetches and returns a Pattern (object) interpreted by the current Matcher.

Example 1

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class PatternExample {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter your date of birth (MM/DD/YYY)");
      String date = sc.next();
      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);
      //Creating a Matcher object
      Matcher matcher = pattern.matcher(date);
      //Validating the date
      if(matcher.matches())
         System.out.println("Date is valid");
      else
         System.out.println("Date is not valid");
      //Retrieving Pattern used
      Pattern p = matcher.pattern();
      System.out.println("Pattern used to match the given date: \n"+p);
   }
}

Output

Enter your date of birth
01/21/2019
Date is valid
Pattern used to match the given date:
^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$

Example 2

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class PatternExample {
   public static void main(String args[]) {
      //Reading String from user
      System.out.println("Enter a String");
      Scanner sc = new Scanner(System.in);
      String input = sc.next();
      //Regular expression to match word that starts with a digit
      String regex = "^[0-9].*$";
      //Compiling the regular expression
      Pattern pattern = Pattern.compile(regex);
      //Retrieving the matcher object
      Matcher matcher = pattern.matcher(input);
      Pattern p = matcher.pattern();
      System.out.println("Pattern used to match the given input string: "+p);
      //verifying whether match occurred
      if(matcher.matches())
         System.out.println("First character is a digit");
      else
         System.out.println("First character is not a digit");
   }
}

Output

Enter a String
2sample
Pattern used to match the given input string: ^[0-9].*$
First character is a digit
raja
Published on 20-Nov-2019 06:25:22
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