Re: Protected and package in iterface

From:
Lew <lew@lewscanon.com>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 18 Dec 2007 22:51:52 -0500
Message-ID:
<wvudnTMfx7TFCPXanZ2dnUVZ_tKinZ2d@comcast.com>
Joshua Cranmer <Pidgeo...@verizon.invalid> wrote:

While not quite the same thing, this should be sufficient:

public class Car {
     class PackageView implements Serviceable, Warranteeable {
         // Methods, etc.
     }

     PackageView getPackageView() {
         return new PackageView();
     }

}

It's a cheap-ish hack, but it does a fair job of emulating C++'s
protected or private inheritance.


tam@milkyway.gsfc.nasa.gov wrote:

I'm sure there are ways to get around this but it seems like a lot of
work. E.g., wouldn't this mean that I need to define a PackageView
class inside each vehicle type (Bicycle, Trolley, Boat...)? It does
seem a bit hackish to me... It seems to obfuscate what would be a
straightforward inheritance tree.


Whatever. It took me about 15 minutes to work up this SSCCE in 3 files:

// testit/InnerFace.java
package testit;

/* p-p */ interface InnerFace
{
   public void foo();
}

// testit/Fimpl.java
package testit;

/** Fimpl - .
  */
public class Fimpl implements Runnable
{
   /** Keep the interface on the down-low.
    */
   /* p-p */ static class NestedFimpl implements InnerFace
   {
     @Override
     public void foo()
     {
       System.out.println( "NestedFimpl.foo()" );
     }
   }

   private volatile InnerFace face;

   /** No-arg constructor.
    */
   public Fimpl()
   {
     this( null );
   }

   /* p-p */ Fimpl( InnerFace f )
   {
     face = (f == null? new NestedFimpl() : f);
   }

   /* p-p */ void setFace( InnerFace f )
   {
     face = (f == null? new NestedFimpl() : f);
   }

   /* p-p */ InnerFace getFace()
   {
     return face;
   }

   /** Delegate an action to <code>foo()</code>.
    */
   @Override
   public void run()
   {
     face.foo();
   }

   /** Main method.
    * @param args <code>String []</code> program arguments.
    */
   public static void main( String[] args )
   {
     Fimpl fimpl = new Fimpl();
     fimpl.getFace().foo();
     fimpl.run();
     fimpl.setFace( new InnerFace()
     {
        @Override
        public void foo()
        {
          System.out.println( " AnonyFace.foo()" );
        }
     });
     fimpl.run();
   }
}

// testit/other/TestFimpl.java
package testit.other;

import testit.Fimpl;

/** TestFimpl - .
  */
public class TestFimpl
{
   /** Main method.
    * @param args <code>String []</code> program arguments.
    */
   public static void main( String [] args)
   {
     Fimpl fimpl = new Fimpl();
     // InnerFace face = fimpl.getFace(); // not enough access rights
     fimpl.run();
   }
}

--
Lew

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