Generic types are custom classes, structures, and enumerations that can work with any type, in a similar way to Array and Dictionary.
Here are the things that you can’t do with generics.
* Call the constructor. new T() is not allowed because at runtime it would be new Object().
* Create an array of that static type. This one is the most annoying, but it makes sense because you’d be creating an array of Objects.
* Call instanceof. This is not allowed because at runtime List<Integer> and List<String> look the same to Java thanks to type erasure.
* Use a primitive type as a generic type parameter. This isn’t a big deal because you can use the wrapper class instead. If you want a type of int, just use Integer.
* Create a static variable as a generic type parameter. This is not allowed because the type is linked to the instance of the class.