What does ABC object=new DEF means ?

Question

When ABC is a parent class and DEF is a child class, and when we define an object in main as :- ABC object= new DEF; Then what does it means ?

Answer 1

I think the statement is ABC object=new DEF() . This means that object is declared to be of type ABC but it refers to a DEF type object. So ABC is declared type and DEF is actual type.

Answer 2

sorry for flooding the answer screen. My connection was down.
Declared type and Actual type come into play in static and dynamic binding.
The logic is simple. Inheritance follows a "is-a" relation. Suppose a class Manager inherits from a class Employee( idea copied from Core Java Vol I by Cay S.Horstmann and Gary Cornell)
If a statement such as this is encountered
Employee a =new Manager();
a is an Employee. an Employee can either be a normal Employee or a Manager.
Suppose class Manager overrides a method getSalary()
If we call
a.getSalary()
the getSalary() of Manager class is called.
This is dynamic binding.
However if there is a static method of any class which is overridden as
1. static String getGrade(Employee e)
2.static String getGrade(Manager e)
Now if we call
getGrade(a);
the getGrade(Employee e) is called not the other one.
This is static binding.
However if we declare
Manager a =new Employee()
it will give an error as a being a Manager cannot refer to a regular Employee.

Answer 3

I think the statement is ABC object=new DEF() . This means that object is declared to be of type ABC but it refers to a DEF type object. So ABC is declared type and DEF is actual type.

Answer 4

I think the statement is ABC object=new DEF() . This means that object is declared to be of type ABC but it refers to a DEF type object. So ABC is declared type and DEF is actual type.

Answer 5

thanks .. but what is meant by declared and actual type and what is the difference between them ?

Answer 6

thanks for the explanation ... now I get the idea