Java Regular Expression : Matcher & Pattern

• Java provides java.util.regex package for regular expression evaluation.
• It has one interface  MatchResault and two derived classes Matcher and Pattern.

 

Testing Matcher and Pattern:-

• The following demo code shows use of Matcher and Pattern class use.It also shows the ISBN code validation.
• A ISBN book code is 13 digit number.

  RegularExpressionDemo.java,

package com.sandeep.regular.exp;

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

public class RegularExpressionDemo {
 
 public static void main(String [] args){
  
  /*matches the input pattern with entire region*/
   Pattern buildPattern = Pattern.compile("p*S");
   Matcher matcher = buildPattern.matcher("pppppS");
   boolean flag = matcher.matches();
   
   System.out.println("Region Matches : "+ flag);
   
   /*replacing first appearnce of p* with 'sandeep' text*/
   Pattern groupPattern = Pattern.compile("p*");
   Matcher stringMatcher = groupPattern.matcher("pppp ter pppp ter pppp abc");
   String modified = stringMatcher.replaceFirst("sandeep");
   
   System.out.println("Modified String: "+modified);
   
   /*A 13 digit ISBN number validation and extraction*/
   Pattern pattern = Pattern.compile("(\d-?){13}");
   Matcher isbnMatcher = pattern.matcher("ISBN: 978-0-12-345678-9");
   while (isbnMatcher.find()){
       System.out.println("ISBN Number is valid and number is : "+isbnMatcher.group());
   }

 }
}