hi i have class called userdata which returns the Userarraylist which is of type User. when ever i try to use contains method to check particular property is existing or not it always returns false why?

Actually i want the array list to be generic which should return the objects that are set in array list.

String className = data.getUserData().get(0).getClass().getSimpleName();

if(className.equalsIgnoreCase("User")) {
   ArrayList<User> userdata=new ArrayList(); 
   userdata = data.getUserData();
   System.out.println(data.getUserData().contains(u.getUserId())); 

   if(userdata.contains(u.getUserName())) {
      System.out.println(userdata.get(0).getEmailId()); 
   }
}