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POIs there a way to use the Delegation design pattern without losing substitutability in Java?
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copied!<p>This question refers to the <strong>Delegation</strong> design pattern found <a href="http://en.wikipedia.org/wiki/Delegation_pattern" rel="nofollow">here</a>.</p> <p>I have a number of interfaces for my game engine representing various entities:</p> <ul> <li>Player</li> <li>Vehicle</li> <li>Mesh</li> <li>etc.</li> </ul> <p>and each one of these can be rendered, so they implement the Renderable interface which contains the method <code>render()</code>.</p> <p><strong>METHOD 1</strong></p> <p>Using delegation, an example looks like this:</p> <pre><code>public interface Vehicle { public void drive(); } public class Car implements Vehicle { public Renderable renderable; @Override public void drive() { // ... } } </code></pre> <p>Whenever I want to render a car, I just call <code>car.renderable.render();</code>.</p> <p>The problem with this method is that I cannot create a List and iterate through it.</p> <p><strong>METHOD 2</strong></p> <p>To solve this, I could have Vehicle extend Renderable:</p> <pre><code>public interface Vehicle extends Renderable { public void drive(); } </code></pre> <p>but the problem with this is that if I define Car, Bicycle, Truck, Tank, etc. each of these classes will have to fill in the code for render() (which will probably be identical).</p> <p>Is there a way to maintain the benefits of extending Renderable in my Vehicle interface without being forced to define render() in all of my concrete classes implementing Vehicle?</p>

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