Finding all words that start with an 'a' in Java

Rishi Raj

Answered on 19th Feb, 2019

All the words that start with a can be found in a string by using regular expressions in Java. The regular expressions are character sequences that can be used to match other strings using a specific pattern syntax. The regular expressions are available in the java.util.regex package which has many classes but the most important are Pattern class and Matcher class.

A program that finds all words that start with an 'a' is using regular expressions is given as follows:

Example

 Live Demo

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Demo {
   public static void main(String args[]) throws Exception {
      String str = "This is an apple";
      String regex = "\\ba\\w*\\b";
      Pattern p = Pattern.compile(regex);
      Matcher m = p.matcher(str);
      String word = null;
      System.out.println("The input string is: " + str);
      System.out.println("The Regex is: " + regex + "\r\n");
      System.out.println("The words that start with a in above string are:");
      while (m.find()) {
         word = m.group();
         System.out.println(word);
      }
      if (word == null) {
         System.out.println("There are no words that start with a");
      }
   }
}

Output

The input string is: This is an apple
The Regex is: \ba\w*\b
The words that start with a in above string are:
an
apple