Yes, you can connect to Gmail using IMAP and POP3. In other words, you can use any (?) IMAP/POP3 client, such as Mozilla Thunderbird or Outlook. You can also write your own client using Java IMAP client.

Yes you can
here is an example I made for college project, try change the yahoo server to Gmail server

      import java.io.BufferedReader;
      import java.io.IOException;
      import java.io.InputStreamReader;
      import java.io.OutputStreamWriter;
      import java.io.PrintWriter;
      import java.net.Socket;
      import java.net.UnknownHostException;
      import javax.swing.JOptionPane;

      public class Email {




      public static void main(String[] args) throws UnknownHostException,IOException    {


      Socket so = new Socket("smtp.mail.yahoo.com",25); // you change this to google's email sever   

         BufferedReader inputStream = new BufferedReader(new InputStreamReader(so.getInputStream()));
PrintWriter outputStream   = new PrintWriter(new OutputStreamWriter(so.getOutputStream()),true);    




    String enemail   =  JOptionPane.showInputDialog(null, "Enter your e-mail in BASEA64 code");
    String password  =  JOptionPane.showInputDialog(null, "Enter your password in BASEA64 code");
    String from      =  JOptionPane.showInputDialog(null, "From");
    String to        =  JOptionPane.showInputDialog(null, "To");
    String subject   =  JOptionPane.showInputDialog(null, "Subject");
    String msg       =  JOptionPane.showInputDialog(null, "Message");

    outputStream.println("HELO ");      
    System.out.println(inputStream.readLine());



    outputStream.println("AUTH LOGIN");     
    System.out.println(inputStream.readLine());


    //You enter your e-mail here , in BASE64 code

    outputStream.println(enemail);      
    System.out.println(inputStream.readLine());


    //You enter your password here , in BASE64 code
    outputStream.println(password);     
    System.out.println(inputStream.readLine());


    outputStream.println("VRFY");       
    System.out.println(inputStream.readLine());

    outputStream.println("MAIL FROM:<"+from+">");       
    System.out.println(inputStream.readLine());


    outputStream.println("RCPT TO:<"+to+">");       
    System.out.println(inputStream.readLine());

    outputStream.println("DATA");       
    System.out.println(inputStream.readLine());


    outputStream.println("Subject:"+subject);
    outputStream.println("FROM :<"+from+">");
    outputStream.println("TO :<"+to+">");
    outputStream.println(msg);
    outputStream.println("");       
    outputStream.println(".");      
    so.close();




             }


 }