Why is it wrong to supply type parameter in the constructor of a generic class (Java)?

Question

I\'m just learning about generics in Java from a textbook, where it talks about a class GenericStack implemented with an ArrayList

Answer 1

Both the class and the constructor can be generic on their own, i.e. each has its own type parameters. For example

class A
{
    A(S s){}
}

To invoke the constructor with all explicit type arguments

new A("abc");  // T=Integer, S=String

Think of it like this, A is the concrete class, and A is the concrete constructor.

Because of type inference, we can omit the type argument for the constructor

new A("abc");  // S=String is inferred

The type argument for the class can also be omitted and inferred, by "diamond" (<>) syntax

A a = new A<>("abc");  // T=Integer is inferred, as well as S=String

I wrote a (long) post on this subject - https://stackoverflow.com/a/32292707/2158288