public static boolean validarEmail(String email) {
    Pattern pattern = Patterns.EMAIL_ADDRESS;
    return pattern.matcher(email).matches();
}

Pattern email_rj = Pattern.compile("^[a-z0-9]+([.][a-z0-9]+)*[@]+[a-z0-9]+[.]+[a-z]{3,4}$");
    boolean valid_em = email_rj.matcher("hola@dominio.com").matches();

public final static boolean isValidEmail(CharSequence email) {
    if (email== null) return false;
    return android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches();
}