Filtrar emails GMAIL

package emailtest;

import java.security.Security;
import java.util.List;
import java.util.Properties;
import javax.mail.Flags;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.NoSuchProviderException;
import javax.mail.Session;
import javax.mail.Store;

/**
 *
 * @author Juno
 */
public class EmailReceiver
{

  public static final Flags.Flag
      DELETED = Flags.Flag.DELETED,
      SEEN = Flags.Flag.SEEN,
      RECENT = Flags.Flag.RECENT,
      ANSWERED = Flags.Flag.ANSWERED;

  public static final String
      GMAIL_POP_SERVER = "pop.gmail.com";

  public static final int
      GMAIL_POP_SERVER_PORT = 995;

  private String popServer,
      user, passwd, foldername;

  private int port;

  private Session session;

  private Folder folder;

  private Store store;

  private Message[] msgs;


  public EmailReceiver()
  {
    popServer = null;
    user = null;
    passwd = null;
    foldername = null;
    session = null;
    store = null;
    folder = null;
    port = GMAIL_POP_SERVER_PORT;
  }

  public EmailReceiver(String popServer, String user, String passwd)
  {
    this.popServer = popServer;
    this.user = user;
    this.passwd = passwd;
    session = null;
    store = null;
    folder = null;
    foldername = "INBOX";
  }

  public EmailReceiver folderName(String folder)
  {
    this.foldername = folder;
    return this;
  }

  public String folderName()
  {
    return foldername;
  }

  public EmailReceiver folder(Folder f)
  {
    folder = f;
    return this;
  }

  public Folder folder()
  {
    return folder;
  }

  public EmailReceiver port(int port)
  {
    this.port = port;
    return this;
  }

  public int port()
  {
    return port;
  }

  public EmailReceiver user(String user)
  {
    this.user = user;
    return this;
  }

  public String user()
  {
    return user;
  }

  public EmailReceiver password(String passwd)
  {
    this.passwd = passwd;
    return this;
  }

  public EmailReceiver server(String server)
  {
    this.popServer = server;
    return this;
  }

  public String server()
  {
    return popServer;
  }

  public EmailReceiver session(Session session)
  {
    this.session = session;
    return this;
  }

  public Session session()
  {
    return session;
  }

  public EmailReceiver store(Store store)
  {
    this.store = store;
    return this;
  }

  public Store store()
  {
    return store;
  }

  public Session createSession(Properties props)
  {
    return Session.getDefaultInstance(props);
  }

  public Session createSession()
  {
    return Session.getDefaultInstance(System.getProperties());
  }

  public Store createStore(boolean ssl)
  {
    if(session == null)
      session = this.createSession();

    Store s = null;
    if(!ssl)
      try {
        return session.getStore("pop3");
      } catch (NoSuchProviderException ex) {
        ex.printStackTrace();
        return null;
      }

    Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
    String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";
    session.getProperties()
        .setProperty("mail.pop3.socketFactory.class", SSL_FACTORY);
    session.getProperties()
        .setProperty("mail.pop3.socketFactory.fallback", "false");

    try {
      return session.getStore("pop3");
    } catch(NoSuchProviderException ex) {
      ex.printStackTrace();
      return null;
    }
  }

  private boolean checkConfig()
  {
    if(popServer == null || popServer.equals(""))
      return false;
    if(user == null || user.equals(""))
      return false;
    if(passwd == null || passwd.equals(""))
      return false;

    return true;
  }

  public EmailReceiver receive()
  {
    if(!checkConfig())
      throw new IllegalStateException(
          "EmailReceiver is not configured!");

    if(session == null)
      session = this.createSession();

    if(store == null)
      store = this.createStore(true);

    if(!store.isConnected())
      try {
        store.connect(popServer, port, user, passwd);
      } catch (MessagingException ex) {
        throw new IllegalStateException(ex.getMessage());
      }

    try {
      folder = store.getFolder(foldername);
      folder.open(Folder.READ_WRITE);
      msgs = folder.getMessages();
    } catch (MessagingException ex) {
      throw new IllegalStateException(ex.getMessage());
    }

    return this;
  }


  public boolean mark(Message[] messages, Flags.Flag flag, boolean set)
  {
    if(messages == null || messages.length == 0)
      throw new IllegalArgumentException(
          "Messages to be setted must be NOT NULL");
    if(flag == null)
      throw new IllegalArgumentException(
          "Flag to be setted must be NOT NULL");

    try {
      folder.setFlags(msgs, new Flags(flag), set);
      return true;
    } catch (MessagingException ex) {
      ex.printStackTrace();
      return false;
    }
  }

  public Message[] getMessages()
  {
    return msgs;
  }


  public static void main(String[] args) throws MessagingException
  {
    EmailReceiver rec = new EmailReceiver();
    rec.server(GMAIL_POP_SERVER)
        .port(GMAIL_POP_SERVER_PORT)
        .user("[email removido]")
        .password("********")
        .folderName("Drive Virtual")
        .receive();

    System.out.println(rec.folder());

    System.out.println(rec.getMessages().length + " Messages!");
  }

}

INBOX
258 Messages!

Exception in thread "main" java.lang.IllegalStateException: folder is not INBOX
        at emailtest.EmailReceiver.receive(EmailReceiver.java:228)
        at emailtest.EmailReceiver.main(EmailReceiver.java:262)
Java Result: 1