/**   @version 1.01 2004-05-11   @author Cay Horstmann*/import java.util.*;import java.util.regex.*;/**   This program tests regular expression matching.   Enter a pattern and strings to match, or hit Cancel   to exit. If the pattern contains groups, the group   boundaries are displayed in the match.*/public class RegExTest{   public static void main(String[] args)   {      Scanner in = new Scanner(System.in);      System.out.println("Enter pattern: ");      String patternString = in.nextLine();      Pattern pattern = null;      try      {         pattern = Pattern.compile(patternString);      }      catch (PatternSyntaxException e)      {         System.out.println("Pattern syntax error");         System.exit(1);      }      while (true)      {         System.out.println("Enter string to match: ");         String input = in.nextLine();                 if (input == null || input.equals("")) return;         Matcher matcher = pattern.matcher(input);         if (matcher.matches())         {            System.out.println("Match");            int g = matcher.groupCount();            if (g > 0)            {               for (int i = 0; i < input.length(); i++)               {                  for (int j = 1; j <= g; j++)                     if (i == matcher.start(j))                         System.out.print('(');                  System.out.print(input.charAt(i));                  for (int j = 1; j <= g; j++)                     if (i + 1 == matcher.end(j))                         System.out.print(')');               }               System.out.println();            }         }         else            System.out.println("No match");      }   }}