Question

Are the following method declarations,

public void testMethod(ArrayList<T extends Animal> list)

and

public <T extends Animal> void testMethod(ArrayList<T> list)

the same?

Answer 1

The difference is that the former does not compile, while the latter does. Is it what you were asking?

If you meant difference between:

public void testMethod (ArrayList <? extends Animal> list)

and

public <T extends Animal> void testMethod (ArrayList <T> list)

then the difference is that in first case you cannot refer to actual type of ArrayList elements, while in second case you can.

Probably, the difference will be more obvious if we will consider the following two cases:

public void testMethod (
    ArrayList <? extends Animal> l1, 
    ArrayList <? extends Animal> l2)

and

public <T extends Animal> void testMethod (
    ArrayList <T> l1, ArrayList <T> l2)

In the first case, first argument is an ArrayList of some type that extends Animal, the second argument is an Arraylist or some (probably other) type that extends Animal.

In the second case, both arguments are ArralLists of the same type that extends Animal.