You can use following utility class to conect to Gmail. Since Gmail only supports POP3 connection with SSL, the connection is established via SSL.

 package org.javatipsjavaemaillistimporter;

import com.sun.mail.pop3.POP3SSLStore;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.Properties;
import javax.mail.Address;
import javax.mail.FetchProfile;
import javax.mail.Flags;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Part;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.URLName;
import javax.mail.internet.ContentType;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.ParseException;

public class GmailUtilities {
    
    private Session session = null;
    private Store store = null;
    private String username, password;
    private Folder folder;
    
    public GmailUtilities() {
        
    }
    
    public void setUserPass(String username, String password) {
        this.username = username;
        this.password = password;
    }
    
    public void connect() throws Exception {
        
        String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";
        
        Properties pop3Props = new Properties();
        
        pop3Props.setProperty("mail.pop3.socketFactory.class", SSL_FACTORY);
        pop3Props.setProperty("mail.pop3.socketFactory.fallback", "false");
        pop3Props.setProperty("mail.pop3.port",  "995");
        pop3Props.setProperty("mail.pop3.socketFactory.port", "995");
        
        URLName url = new URLName("pop3", "pop.gmail.com", 995, "",
                username, password);
        
        session = Session.getInstance(pop3Props, null);
        store = new POP3SSLStore(session, url);
        store.connect();
        
    }
    
    public void openFolder(String folderName) throws Exception {
        
        // Open the Folder
        folder = store.getDefaultFolder();
        
        folder = folder.getFolder(folderName);
        
        if (folder == null) {
            throw new Exception("Invalid folder");
        }
        
        // try to open read/write and if that fails try read-only
        try {
            
            folder.open(Folder.READ_WRITE);
            
        } catch (MessagingException ex) {
            
            folder.open(Folder.READ_ONLY);
            
        }
    }
    
    public void closeFolder() throws Exception {
        folder.close(false);
    }
    
    public int getMessageCount() throws Exception {
        return folder.getMessageCount();
    }
    
    public int getNewMessageCount() throws Exception {
        return folder.getNewMessageCount();
    }
    
    public void disconnect() throws Exception {
        store.close();
    }
    
    public void printMessage(int messageNo) throws Exception {
        System.out.println("Getting message number: " + messageNo);
        
        Message m = null;
        
        try {
            m = folder.getMessage(messageNo);
            dumpPart(m);
        } catch (IndexOutOfBoundsException iex) {
            System.out.println("Message number out of range");
        }
    }
    
    public void printAllMessageEnvelopes() throws Exception {
        
        // Attributes & Flags for all messages ..
        Message[] msgs = folder.getMessages();
        
        // Use a suitable FetchProfile
        FetchProfile fp = new FetchProfile();
        fp.add(FetchProfile.Item.ENVELOPE);        
        folder.fetch(msgs, fp);
        
        for (int i = 0; i < msgs.length; i++) {
            System.out.println("--------------------------");
            System.out.println("MESSAGE #" + (i + 1) + ":");
            dumpEnvelope(msgs[i]);
            
        }
        
    }
    
    public void printAllMessages() throws Exception {
     
        // Attributes & Flags for all messages ..
        Message[] msgs = folder.getMessages();
        
        // Use a suitable FetchProfile
        FetchProfile fp = new FetchProfile();
        fp.add(FetchProfile.Item.ENVELOPE);        
        folder.fetch(msgs, fp);
        
        for (int i = 0; i < msgs.length; i++) {
            System.out.println("--------------------------");
            System.out.println("MESSAGE #" + (i + 1) + ":");
            dumpPart(msgs[i]);
        }
        
    
    }
    
    
    public static void dumpPart(Part p) throws Exception {
        if (p instanceof Message)
            dumpEnvelope((Message)p);
       
        String ct = p.getContentType();
        try {
            pr("CONTENT-TYPE: " + (new ContentType(ct)).toString());
        } catch (ParseException pex) {
            pr("BAD CONTENT-TYPE: " + ct);
        }
        
        /*
         * Using isMimeType to determine the content type avoids
         * fetching the actual content data until we need it.
         */
        if (p.isMimeType("text/plain")) {
            pr("This is plain text");
            pr("---------------------------");
            System.out.println((String)p.getContent());        
        } else {
            
            // just a separator
            pr("---------------------------");
            
        }
    }
    
    public static void dumpEnvelope(Message m) throws Exception {        
        pr(" ");
        Address[] a;
        // FROM
        if ((a = m.getFrom()) != null) {
            for (int j = 0; j < a.length; j++)
                pr("FROM: " + a[j].toString());
        }
        
        // TO
        if ((a = m.getRecipients(Message.RecipientType.TO)) != null) {
            for (int j = 0; j < a.length; j++) {
                pr("TO: " + a[j].toString());                
            }
        }
        
        // SUBJECT
        pr("SUBJECT: " + m.getSubject());
        
        // DATE
        Date d = m.getSentDate();
        pr("SendDate: " +
                (d != null ? d.toString() : "UNKNOWN"));
        

    }
    
    static String indentStr = "                                               ";
    static int level = 0;
    
    /**
     * Print a, possibly indented, string.
     */
    public static void pr(String s) {
        
        System.out.print(indentStr.substring(0, level * 2));
        System.out.println(s);
    }
    
}

And the following code snippet shows how to use the above utility class. You can uncomment printAllMessageEnvelopes() method to just print the envelopes of the messages instead of whole messages.
package org.javatipsjavaemaillistimporter;

public class Main {
    
    /** Creates a new instance of Main */
    public Main() {
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        
        try {
            
            GmailUtilities gmail = new GmailUtilities();
            gmail.setUserPass("This email address is being protected from spambots. You need JavaScript enabled to view it.", "mypassword");
            gmail.connect();
            gmail.openFolder("INBOX");
            
            int totalMessages = gmail.getMessageCount();
            int newMessages = gmail.getNewMessageCount();
            
            System.out.println("Total messages = " + totalMessages);
            System.out.println("New messages = " + newMessages);
            System.out.println("-------------------------------");
            
            //gmail.printAllMessageEnvelopes();
            gmail.printAllMessages();
            
        } catch(Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
        
    }
    
}