Hi,
Have a look at the below code and let me know if it helped you or if you have any further queries.

/**
* Program to scan email address from a file and write into an other file
*/
import java.io.*;
import java.util.regex.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Scanner;
import java.util.StringTokenizer;

/**
* @author helper
*
*/
public class EmailExtractor {

ArrayList<String> emailsList = new ArrayList<String>();

public static void main(String[] args) {
EmailExtractor ex = new EmailExtractor();
ex.fileScanner();
}


public void fileScanner() {
String fileName = "emailAddress";
String line = null;
String email="";
try {
File file = new File(fileName);
FileReader fileReader = new FileReader(file);
BufferedReader reader = new BufferedReader(fileReader);
/*** Build a pattern of email address */
String regex ="^[\\w\\._-]+[@{1}]+[a-z+\\.{1,3}]+[a-z]$";
/***
* Explanation of RE: email address starts with alpha numeric characters,has '@'
* and has '.'at least once and to the max of three
* can also contain '_' '-'
* and ends with characters from a-z
* */
Pattern p = Pattern.compile(regex);
/*** Read each line of the line and break each line into tokens to see if it matches the pattern*/

while ((line = reader.readLine()) != null) {
StringTokenizer st = new StringTokenizer(line);
while(st.hasMoreTokens()){
String token = st.nextToken();
Matcher m = p.matcher(token);
boolean result = m.matches();
/*** If a token matches the pattern, collect all the email address into an arrayList
* and use it later to write into an other file */
if(result){
email = m.group();
emailsList.add(email);
}
}
}
reader.close();
} catch (IOException ex) {
ex.printStackTrace();
}
/*** write the email address to an other file. */
makeEmailList(emailsList);
}

public void makeEmailList(ArrayList emailArray){
String email="";
try{
FileWriter writer = new FileWriter("emailList.txt");
for(Iterator iter = emailArray.iterator(); iter.hasNext();){
email = (String) iter.next();
//System.out.println("email = "+email);
writer.write(email);
writer.write("\n");
}
writer.close();
}catch(IOException ex){
ex.printStackTrace();
}
}
}
------------------------------------------------------
a text file named: emailAddress.txt

Hi,

How are you doing?
I came to know you need help in writing a program.
I am woriking on it.
My email address is [email protected] or [email protected]
If any more queries, feel free to contact to my above email address.

Regards,
Helper.
-------------------------------------------------------
output in a file named emailList.txt

[email protected]
[email protected]