public void generateExcelAndSendEmail(){
    Map<String,ArrayList> map = new HashMap<>();
    ArrayList<String> StudentID = new ArrayList<String>();
    ArrayList<String> Subject = new ArrayList<>();
    ArrayList<String> conducted = new ArrayList<String>();
    ArrayList<String> totalattended = new ArrayList<>();
    ArrayList<String> percentage = new ArrayList<String>();
    ArrayList<String> TeacherID = new ArrayList<>();
    StudentID = getIntent().getStringArrayListExtra("StudentID");
    Subject = getIntent().getStringArrayListExtra("Subject");
    conducted = getIntent().getStringArrayListExtra("conducted");
    totalattended = getIntent().getStringArrayListExtra("totalattended");
    percentage = getIntent().getStringArrayListExtra("percentage");
    TeacherID = getIntent().getStringArrayListExtra("TeacherID");

    File sd = Environment.getExternalStorageDirectory();
    final String xlfile = "ExportedData.xls";

    File directory = new File(sd.getAbsolutePath());
    //create directory if not exist
    if (!directory.isDirectory()) {
        directory.mkdirs();
    }
    File file = new File(directory, xlfile);
    try {

        //file path

        WorkbookSettings wbSettings = new WorkbookSettings();
        wbSettings.setLocale(new Locale("en", "EN"));
        WritableWorkbook workbook;
        workbook = Workbook.createWorkbook(file, wbSettings);
        //Excel sheet name. 0 represents first sheet
        WritableSheet sheet = workbook.createSheet("Attendance", 0);
        // column and row
        sheet.addCell(new Label(0, 0, "UserName"));
        sheet.addCell(new Label(1, 0, "PhoneNumber"));


    Set<String> studs = new HashSet<>(StudentID);
    for(int i=0;i<studs.size();i++){

        for(int j=0;j<StudentID.size();j++){

        }
    }

    workbook.write();
    workbook.close();


    } catch(Exception e){
        e.printStackTrace();
    }


    try {
        final String[] attach=new String[1];
        attach[0]=file.getAbsolutePath();
        Thread t = new Thread(new Runnable() {
            @Override
            public void run() {
                try {

                    GMailSender sender = new GMailSender("myemail@gmail.com", "mypassword");
                    sender.sendMail("This is Subject",
                            "This is Body",
                            "someEmail@gmail.com",
                            "someEmail@gmail.com");

            } catch (Exception e) {
                    Log.d("email error",e.getMessage());
                    e.printStackTrace();
                }
            }
        });

    } catch (Exception e) {
        Log.d("email error",e.getMessage());
        e.printStackTrace();
    }

   // Toast.makeText(getApplicationContext(),"Email sent successfully",Toast.LENGTH_LONG).show();
}

import android.util.Log;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.Security;
import java.util.Properties;

import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.mail.Message;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class GMailSender extends javax.mail.Authenticator {
private String mailhost = "smtp.gmail.com";
private String user;
private String password;
private Session session;

static {
    Security.addProvider(new com.alleviate.attendence.emailHelper.JSSEProvider());
}

public GMailSender(String user, String password) {
    this.user = user;
    this.password = password;

    Properties props = new Properties();
    props.setProperty("mail.transport.protocol", "smtp");
    props.setProperty("mail.host", mailhost);
    props.put("mail.smtp.auth", "true");
    props.put("mail.smtp.port", "465");
    props.put("mail.smtp.socketFactory.port", "465");
    props.put("mail.smtp.socketFactory.class",
            "javax.net.ssl.SSLSocketFactory");
    props.put("mail.smtp.socketFactory.fallback", "false");
    props.setProperty("mail.smtp.quitwait", "false");

    session = Session.getDefaultInstance(props, this);
}

protected PasswordAuthentication getPasswordAuthentication() {
    return new PasswordAuthentication(user, password);
}

public synchronized void sendMail(String subject, String body, String sender, String recipients) throws Exception {
    try{
        MimeMessage message = new MimeMessage(session);
        DataHandler handler = new DataHandler(new ByteArrayDataSource(body.getBytes(), "text/plain"));
        message.setSender(new InternetAddress(sender));
        message.setSubject(subject);
        message.setDataHandler(handler);
        if (recipients.indexOf(',') > 0)
            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipients));
        else
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(recipients));
        Transport.send(message);
    }catch(Exception e){
        Log.d("email error",e.getMessage());
    }
}

public class ByteArrayDataSource implements DataSource {
    private byte[] data;
    private String type;

    public ByteArrayDataSource(byte[] data, String type) {
        super();
        this.data = data;
        this.type = type;
    }

    public ByteArrayDataSource(byte[] data) {
        super();
        this.data = data;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getContentType() {
        if (type == null)
            return "application/octet-stream";
        else
            return type;
    }

    public InputStream getInputStream() throws IOException {
        return new ByteArrayInputStream(data);
    }

    public String getName() {
        return "ByteArrayDataSource";
    }

    public OutputStream getOutputStream() throws IOException {
        throw new IOException("Not Supported");
    }
}
}

import java.security.AccessController;
import java.security.Provider;

public final class JSSEProvider extends Provider {

public JSSEProvider() {
    super("HarmonyJSSE", 1.0, "Harmony JSSE Provider");
    AccessController.doPrivileged(new java.security.PrivilegedAction<Void>() {
        public Void run() {
            put("SSLContext.TLS",
                    "org.apache.harmony.xnet.provider.jsse.SSLContextImpl");
            put("Alg.Alias.SSLContext.TLSv1", "TLS");
            put("KeyManagerFactory.X509",
                    "org.apache.harmony.xnet.provider.jsse.KeyManagerFactoryImpl");
            put("TrustManagerFactory.X509",
                    "org.apache.harmony.xnet.provider.jsse.TrustManagerFactoryImpl");
            return null;
        }
    });
}
}