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POOverride beats Overload? Why does that make sense at all?
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  1. POOverride beats Overload? Why does that make sense at all?
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    copied!<p><strong>Why should a super method hand out it's <em>this</em> reference as super type instead of own type?</strong> </p> <p>I don't understand the practicality of this behavior. I learned to code against Types/Interfaces and not against classes, but considering this kind of behavior I'm confused about everything I thought OOP was standing for. This breaks possibility of clean code and forces me to fill it with verbose control flow like heavy use of the <em>instanceof</em> operator. <em>Why does that kind of behavior make even sense?</em> </p> <p><strong>Abstract:</strong><br> Consider this code:</p> <pre><code>abstract class A { public void visit(Target t) { t.method(this); } } </code></pre> <p>If <code>Target</code> overloads <code>method()</code> with A and different child classes of A in it's signature and these children don't override <code>visit(Target t)</code> themselves then overloaded <code>method(A a)</code> will be choosen by compiler always.</p> <p><strong>Working example:</strong> <a href="http://pastebin.com/EGNpY7pF" rel="nofollow">http://pastebin.com/EGNpY7pF</a></p> <p><strong>Code Snip</strong></p> <pre><code>public class Target { public static abstract class A { void visit(Target t) { t.method(this); } } public static class B extends A {} public static class C extends A { @Override void visit(Target t) { t.method(this); } } void method(A a) { System.out.println("A");} void method(B b) { System.out.println("B");} void method(C c) { System.out.println("C");} public static void main(String[] args) { Target t = new Target(); A ab = new B(); B b = new B(); A ac = new C(); C c = new C(); ab.visit(t); b.visit(t); ac.visit(t); c.visit(t); } </code></pre> <p>}</p> <p><strong>Output</strong> A A C C<br> Which is really akward since <code>ac</code> is referenced to as <code>A</code>-Type but still <code>C</code>'s overriden <code>visit()</code> method is called.</p>
 

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