Pattern pattern() method in Java with examples

Java Object Oriented Programming Programming

The java.util.regex package of java provides various classes to find particular patterns in character sequences. The pattern class of this package is a compiled representation of a regular expression.

The pattern() method of the Pattern class fetches and returns the regular expression in the string format, using which the current pattern was compiled.

Example 1

import java.util.regex.Pattern;
public class PatternExample {
   public static void main(String[] args) {
      String date = "12/09/2019";
      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);
      if(pattern.matcher(date).matches()) {
         System.out.println("Date is valid");
      } else {
         System.out.println("Date is not valid");
      }
      //Retrieving the regular expression of the current pattern
      String regularExpression = pattern.pattern();
      System.out.println("Regular expression: "+regularExpression);
   }
}

Output

Date is valid
Regular expression: ^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$

Example 2

public class PatternExample {
   public static void main(String[] args) {
      String input = "Hi my id is 056E1563";
      //Regular expression using groups
      String regex = "(.*)?(\d+)";
      //Creating a pattern object
      Pattern pattern = Pattern.compile(regex);
      if(pattern.matcher(input).matches()) {
         System.out.println("Match found");
      } else {
         System.out.println("Match not found");
      }
      //Retrieving the regular expression of the current pattern
      String regularExpression = pattern.pattern();
      System.out.println("Regular expression: "+regularExpression);
   }
}

Output

Match found
Regular expression: (.*)?(\d+)

Maruthi Krishna

Updated on 20-Nov-2019 05:47:04

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