Where should one write generics in Java?

Question

Java

What generics are for, I basically understand: to get objects of a specific type, and not of the Object type, when accessing the elements of the collection. I just don’t understand why they need to be written twice: Yes, I know that in java 7 you can get by with a diamond, but I still don’t understand why the type is removed in the creation of the collection. Explain the difference between these two lines:
ArrayList<Shape> list = new ArrayList<Shape>();

ArrayList<Shape> list = new ArrayList<Shape>();
ArrayList list = new ArrayList<Shape>();

Thank you in advance.
PS: No, they didn't ban me on Google, though I can't find the answer.

Answer 1

In the first case, you will have an ArrayList typed with the Shape class and you can access the elements as Shape objects.
In the second case, you will also have a typed ArrayList, only it will be typed with the Object class (no matter how you initialized the ArrayList), and if you want to refer to the element as a Shape class, you will have to cast the element to the Shape class.
Well, if it's quite simple.