Mascara email por expressao regular

public void validate(Object value) throws Exception {
   String regex = "([a-zA-Z0-9_\.])+@([a-zA-Z0-9])+\.([a-zA-z])+(\.([a-zA-z])+)*";
   Pattern p = Pattern.compile(regex);
   Matcher m = p.matcher((String)value);
		
   if(!m.matches())
        System.out.println("E-Mail inválido");
}