Re: private instance variable of derived class not always returned by base class getter?

From:

Lew <lew@nospam.lewscanon.com>

Newsgroups:

comp.lang.java.help

Date:

Sun, 01 Apr 2007 11:42:16 -0400

Message-ID:

<EKidnVBoOYNET5LbnZ2dnUVZ_ternZ2d@comcast.com>

Piet wrote:

Conclusions:
1. If I want to access a private instance variable (declared in a
derived class) by a method declared in the superclass, binding of that
private variable to the instance of the derived class must occur in a
base class method, i. e. I must call a "super" method at some point.
2. If I want to access a private instance variable (declared in a
derived class) by a method declared in the derived class (which amy
override a superclass method), it must be explicitly bound to the
instance inside a method declared in the derived class.

I never had to deal with inheritance issues like that, but now, the
more I think about it, the more sense does it make.

Try this:

class Base
{
   private String name;
   public Base()
   {
     this.name = "Base default";
   }

   public Base( String name )
   {
     this.name = name;
   }

   public String getName()
   {
     return this.name;
   }

   public void displayMe()
   {
       System.out.println( "Display me: "+ getName() );
   }
}

public class Derived extends Base
{
   private String name;

   public Derived( String name )
   {
     this.name = name;
   }

   public String getName()
   {
     return this.name;
   }

   public String getBaseName()
   {
       return super.getName();
   }

   public static void main( String [] args )
   {
      Derived d = new Derived( "Derived test" );
      Base b = d;

      System.out.println( "Derived name = "+ d.getName() );
      System.out.println( "Base name = "+ d.getBaseName() );
      System.out.println( "" );

      System.out.println( b.getName() );
      b.displayMe();
   }

}

-- Lew