Any simple way to explain why I cannot do List animals = new ArrayList()? [duplicate]

Answer 1

Notice that if you have

List dogs = new ArrayList()

then, if you could do

List animals = dogs;

this does not turn dogs into a List. The data structure underlying animals is still an ArrayList, so if you try to insert an Elephant into animals, you are actually inserting it into an ArrayList which is not going to work (the Elephant is obviously way too big ;-).