Regular Expression to find multiple email addresses in a file in java

Question

I have a file which have a series of multiple email addresses. I need to separate emails from it using Regex in java. I have taken a sample string and tried like below.

import java.util.HashSet;
import java.util.Set;
import java.io.*;
import java.util.*;
import java.util.regex.*;



public class Email2 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String content = "s.lokesh1729@gmail.com,lokesh.harshitha1729@gmail.com";
        Pattern p = Pattern.compile("^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@"
                + "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$");
        Matcher m = p.matcher(content);
        if(m.find())
        {
            System.out.println(m.group(1));
            System.out.println(m.group(2));
        }
    }

}

The above code doesn't returns anything, but if I changed content to containing only one email address, it returns. I know that I can split it with the comma or any other special character, but I want to do it with Regular Expressions?

Answer 1

You could split the email addresses in content, see below:

String string = "s.lokesh1729@gmail.com,lokesh.harshitha1729@gmail.com";
String[] array= string.split(",");
String array= array[0]; // s.lokesh1729@gmail.com
String array= array[1]; // lokesh.harshitha1729@gmail.com

Then, you could test your email against this expression:

 String REGEX = "([_A-Za-z0-9-]+)(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9-]+)*(\\.[A-Za-z]{2,})";

And here you can see how they're evaluated How to validate email address with regular expression

Snippets below are from URL above.

 EmailValidator.java

  package com.mkyong.regex;

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

  public class EmailValidator {

  private Pattern pattern;
  private Matcher matcher;

private static final String EMAIL_PATTERN = 
    "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@"
    + "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

public EmailValidator() {
    pattern = Pattern.compile(EMAIL_PATTERN);
}

/**
 * Validate hex with regular expression
 * 
 * @param hex
 *            hex for validation
 * @return true valid hex, false invalid hex
 */
public boolean validate(final String hex) {

    matcher = pattern.matcher(hex);
    return matcher.matches();

  }
 }

But finally, here they validate multiple email addresses with a regular expression How to validate multiple email addresses with regular expression in Java

Snippet below is from URL above:

    public static boolean isValid(String email) {
    System.out.println(email + " >>>>>>>> is Valid? " + Pattern.matches(regex, email));
    return Pattern.matches(regex, email);
}

Answer 2

Not sure on Java, but you'd have to sit in a while loop looking for all the
emails.

Something like while( search( Rx, string ) ) { ... }

This is a good regex from here .

"[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*"  

Formatted:

 [a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+ 
 @
 [a-zA-Z0-9] 
 (?:
      [a-zA-Z0-9-]{0,61} 
      [a-zA-Z0-9] 
 )?
 (?:
      \. 
      [a-zA-Z0-9] 
      (?:
           [a-zA-Z0-9-]{0,61} 
           [a-zA-Z0-9] 
      )?
 )*