<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css"> <script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <!------ Include the above in your HEAD tag ----------> @RemoteMethod public Boolean validateemailid(String email){ return isValidEmailAddress(email); } public static boolean isValidEmailAddress(String str) { String at = "@"; String dot = "."; int lat = str.indexOf(at); int lstr = str.length(); if (str.indexOf(at) == -1) { return false; } if (str.indexOf(at) == -1 || str.indexOf(at) == 0 || str.indexOf(at) == lstr) { return false; } if (str.indexOf(dot) == -1 || str.indexOf(dot) == 0 || str.indexOf(dot) == lstr) { return false; } if (str.indexOf(at, (lat + 1)) != -1) { return false; } if (str.substring(lat - 1, lat) == dot || str.substring(lat + 1, lat + 2) == dot) { return false; } if (str.indexOf(dot, (lat + 2)) == -1) { return false; } if (str.indexOf(" ") != -1) { return false; } return true; } }