What is the difference between an actual type and declared type variable?

Answer 1

I believe a declared type is the type used when first declaring a variable.

And the actual type is the type that the variable is actually assigned, which

could be the declared type or any subtype of that type. So given

GeometricObject shape = new Triangle();

GeometricObject is the declared type and Triangle is the actual type. To

demonstrate this more clearly the following statements are all correct.

GeometricObject shape; // shape declared to be a GeometricObject

shape = new Triangle(); // actual type assigned = Triangle

shape = new Square(); // now shape refers to a Square object

This is the basis of polymorphism. It allows you to write methods which have

for parameters more general types but are able to handle subtypes differently.

This makes your code more general and reusable.