Use polymorphism using interfaces

- When you create a variable it has to have a type.…Either you define the type…or it's inferred by the value that is being assigned to it.…When you have a variable that has a type…you define the type based on a class.…Remember, since everything is a class…that means integer, Boolean, string,…and everything else that we used before…to define a variable is also a class.…So if we create a variable that accepts integers…we are typing that variable using the integer class.…

We can type variables to be any object we want,…including objects based on classes that we create ourselves.…So if I take a variable and set it to the cat type…I can create an instance of a cat class…and assign it to the variable.…But what if I wanted to assign a fish to the variable?…Because it is specifically typed to a cat…I can't take an instance of a fish class and assign it.…There is a way to deal with this.…Instead of typing to a cat…I can type the variable to the super class, animal.…

Since, by the definition of the class,…a cat and a fish are both animals…