This Java program reads an input text file and identifies valid email IDs using regular expressions. It forms a pattern for email IDs and checks each string in the file against this pattern. When a match occurs, the program writes the email ID to an output file. By leveraging regular expressions, developers can efficiently extract email addresses from text files, making it a useful tool for data processing and validation.

code:

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

public class EmailExtractor {
    public static void main(String[] args) throws IOException {
        // Regular expression for email ID
        Pattern emailPattern = Pattern.compile("[a-zA-Z0-9][a-zA-Z0-9_.]*@[a-zA-Z0-9]+([.][a-zA-Z]+)+");

        // Read input.txt file
        BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
        String line;
        while ((line = reader.readLine()) != null) {
            Matcher matcher = emailPattern.matcher(line);
            while (matcher.find()) {
                System.out.println(matcher.group());
            }
        }
        reader.close();
    }
}

Output:

[email protected]
[email protected]

To run the Java program that detects email IDs in a text file, follow these steps:

    1.Compile the Java File:

1. • Open your terminal or command prompt.
   • Navigate to the directory containing your Java file (let’s assume it’s named EmailExtractor.java).
   • Compile the Java file using the command

   • javac EmailExtractor.java
     
     
     
     

   2.Create an Input File

• • • Create a text file named “input.txt” (or use an existing one) in the same directory
    • Add some text content with email addresses (valid or invalid)

    3.Run the Program:

1. 1. 1. • Execute the compiled Java program using the command

         • java EmailExtractor