Java示例查找Word出现次数

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

public class Main {
   public static void main(String args[]) throws Exception {
      String candidate = "this is a test, A TEST.";
      String regex = "\\ba\\w*\\b";
      Pattern p = Pattern.compile(regex);
      Matcher m = p.matcher(candidate);

      String val = null;
      System.out.println("INPUT: " + candidate);
      System.out.println("REGEX: " + regex + "\r\n");

      while (m.find()) {
         val = m.group();
         System.out.println("MATCH: " + val);
      }

      if (val == null) {
         System.out.println("NO MATCHES: ");
      }
   }
}