StackOverflow2013

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POHiding instance variables of a class
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copied!<p>I'm wondering why Java has this strange behavior regarding a superclass and a subclass having instance variables with the same name.</p> <p>Let's say we have the following class definitions:</p> <pre><code>class Parent { int var = 1; } class Child extends Parent { int var = 2; } </code></pre> <p>By doing this, we are supposed to have hidden the superclass's variable <code>var</code>. And if we do not explicitly specify a way to access <code>Parent</code>'s <code>var</code> via a <code>super</code> call, then we should never be able to access <code>var</code> from an instance of a child.</p> <p>But when we have a cast, this hiding mechanism breaks:</p> <pre><code>Child child = new Child(); Parent parent = (Parent)child; System.out.println(parent.var); // prints out 1, instead of 2 </code></pre> <p>Doesn't this completely circumvent the whole point of field hiding? If this is the case, then doesn't that render the the idea completely useless?</p> <p><strong>EDIT</strong>: I am referring specifically to <a href="http://download.oracle.com/javase/tutorial/java/IandI/hidevariables.html">this article</a> in the Java Tutorials. It mentions</p> <blockquote> <p>Within the subclass, the field in the superclass <strong>cannot</strong> be referenced by its simple name. Instead, the field <strong>must</strong> be accessed through super...</p> </blockquote> <p>From what I read there, it seems to imply that the developers of Java had some kind of technique in mind in doing this. Though I agree that it is a rather obscure concept and would probably bad practice in general.</p>

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