Use JavaMail to download email headers from GMail and spit out TSV

InboxReader.java

import java.util.Properties;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.NoSuchProviderException;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.FetchProfile;

public class InboxReader 
{  
  public static String combine(String[] s, String glue)
  {
    int k=s.length;
    if (k==0) return null;
    StringBuilder out=new StringBuilder();
    out.append(s[0]);
    for (int x=1;x<k;++x)
      out.append(glue).append(s[x]);
    return out.toString();
  }

  public static void main(String args[]) {
    Properties props = System.getProperties();
    props.setProperty("mail.store.protocol", "imaps");
      try {
        Session session = Session.getDefaultInstance(props, null);
        Store store = session.getStore("imaps");
        store.connect("imap.gmail.com", "USERNAME", "PASSWORD");
        System.out.println(store);
        Folder inbox = store.getFolder("Inbox");
        inbox.open(Folder.READ_ONLY);
        Message messages[] = inbox.getMessages();
        FetchProfile fp = new FetchProfile();
        inbox.fetch(messages, fp);
        for (int i = 0; i < messages.length; i++) {
          String from = messages[i].getFrom();
          String subject = messages[i].getSubject();
          String to = messages[i].getHeader("X-Mailer"); 
          System.out.println(from + "\t" + to + "\t" + subject);
        }
    } catch (NoSuchProviderException e) {
      e.printStackTrace();
      System.exit(1);
    } catch (MessagingException e) {
      e.printStackTrace();
      System.exit(2);
    } 
  }
}