Explicit type conversion

[vpidaparthi]

Here is a way in which we can do type conversions explicitly.
In the following example, class B extends class A.

public class A {

private int aa ;
protected int ab ;
public int ac ;

public void make_it_A(int intparam1){

aa = intparam1;
}
}

public class B extends A {

private int ba ;
protected int bb ;
public int bc ;

public A make_it_A(int aa){

A newA = this;
newA.ba = null;
newA.bb = null;
newA.bc = null;
newA.make_it_A(aa);
return newA;

}
}

instead of doing
A aobject = bObject;
you can do
A aobject = bobject.make_it_A(myInt);

Please express your views about cases where this can be useful if you used this.

[ArchAngel]

I can't really see the point of what you are doing. You are trying to use this strange system in place of proper inheritance and polymorphism. Why would you *ever* want to do this?????

[vpidaparthi]

This new system can be useful when class A represents "Person" and class B extends from "person" and represents a "policeman" . After the office hours the "policeman" is just a "person" with no previleges of a policeman on duty.

Please forward your reply. I would like to know the other ways of handling the same.

[ArchAngel]

No. This still doesn't make much sense. What's wrong with:

  public class Person { // Person methods... }
  public class Policeman extends Person { // Police methods... }

(Actually, in advanced OO design, these are really roles, but I'll leave that for now)

[vpidaparthi]

I am really ignorent compared to you, but how do you prevent a "Person" from invoking methods in "policeman"?

for example, aPerson.arrest_Joe() i.e. A.Bmethod()?

Here, "Person" and "Policeman" are the classes we are giving to the police department and they reuse these classes.

[Fantik]

that doesn't happen. inheritance only goes down.

if you had a person object, they can't invoke methods in a policeman class.

but policemen can invoke methods in a person class.

read up on inheritance.. you are thinking of it incorrectly.

[ArchAngel]

Inheritance doesn't work like that! Here are some slightly more complete definitions:

  public class Person() {
    public Person(String firstName, String surname) {
      this.firstName = firstName;
      this.surname = surname;
    }

    public String getName() {
      return firstName + " " + surname;
    }

    private String firstName;
    private String surname;
 }

  public class Policeman extends Person {
    public Policeman(String firstName, String surname, int hatSize) {
      super(firstName, surname);
      this.hatSize = hatSize;
    }

    public void arrest(Person p) {
      // some code here....
    }
    private int hatSize;
  }

Here is how they would be used:

  public class TestClasses {
    public static void main(String[] args) {
       Person robber = new Person("Robin", "Banks");
       System.out.println("Person: " + robber.getName());

       Policeman pc_plod = new Policeman("Chief", "Wiggum", 12);
       System.out.println("Policeman: " + robber.getName());

       pc_plod.arrest(robber);

       // You can't call robber.arrest(pc_plod).
    }
  }