Thread: Java Inheritance Question...

Hi,
I have a stupid question. Trying to teach myself about Java Inheritance. I have the following classes:

public class A
{
    private int iClassVariableA;
 
    public set_class_VariableA( int iVariable)
    {
        iClassVariableA = iVariable;
    }
}
 
public class B extends A
{
    private int iClassVariableB;
 
    public set_class_VariableB( int iVariable)
    {
        iClassVariableB = iVariable;
    }
}
 
public class C extends A
{
    private int iClassVariableC;
 
    public set_class_VariableC( int iVariable)
    {
        iClassVariableC = iVariable;
    }
}

In my main I have the following:

A[] myA = new A[3];
 
myA[0] = new A();
myA[1] = new B();
myA[2] = new C()';
 
myA[0].set_class_VariableA(0);
myA[1].set_class_VariableA(0);
myA[1].set_class_VariableB(1); // I get a compiler error here
myA[2].set_class_VariableA(0);
myA[2].set_class_VariableC(2); // and here

The error is:
cannot find symbol
myA[1].set_class_VariableB(1);
^
symbol: method set_class_VariableB(int)
location: class A

If I create each instance variable as it's own type:

myA = new A();
myB = new B();
myC = new C()';

everything works fine. My understanding of Java's inheritance says that I should be able to create a variable of class A and assign it to class B... What am I not understanding here?

Thanks,
Tim

Instances of A do not even know that B and C exist. B inherits everything A has and can add to it. C inherits everything A has and can add to it. B and C have a common ancestor (A) but do not share their own methods or variables with each other.

Greg,
Thanks for the response. I think I get it now...