Question

I try use List instead of List

List<?> list = new ArrayList<Integer>();
...
list.add(1); //compile error

What i do wrong and how cast new value to Integer?
Maybe i shoud use List in my project?

Answer 1

List<?> means a list of some type, but we don’t know which type. You can only put objects of the right type into a list – but since you don’t know the type, you in effect can’t put anything in such a list (other than null).

There is no way around this, other than declaring your variable as List<Integer>.