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    <p>You don't want to check the class of an object before doing something with it in your case. You should be using <a href="http://www.uweb.ucsb.edu/~cdecuir/Polymorphism.html" rel="nofollow noreferrer">polymorphism</a>. You want to have the Interface define some methods. Each class implement those methods. Refer to the object by its interface, and have the individual implementations of those objects return their values to the caller.</p> <p>If you describe a few more of the objects you think you need, people here will have opinions on how you should lay them out. But from what you've provided, you may want a "Building" interface that defines some general methods. You may also want a "UsableItem" interface or something more generic. Hospital could be a class that implements building. ReceptionDesk could implement UsableItem. Building could have a grid of UsableItem inside it.</p> <p>If rotate() was a common method to all furniture that actually did some work, you may consider making an AbstractUsableItem class that was an abstract class implementing UsableItemand providing the rotate() method. If rotate was different in each implementing class, you would have that method in the interface, but each class, like ReceptionDesk would do its own thing with the rotate() method. Your code would do something like:</p> <pre><code>UsableItem desk = new ReceptionDesk(); desk.rotate() </code></pre> <p>In your example, if your mouse click on a screen rotated the object under it, and you really did need to check to see if the object could be rotated before doing something like that, you'd do</p> <pre><code>if (clickedObject instanceOf UsableItem) { ((UsableItem) clickedObject).rotate(); } </code></pre> <p>where UsableItem was the interface or abstract class. Some people feel that all design should be done via an interface contract and suggest an interface for every type of class, but I don't know if you have to go that far.</p>
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    1. POWould this be the correct place to use the java keyword "interface"?
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    1. USJohn Ellinwood
    1. USJohn Ellinwood
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    1. COThanks for this useful answer and information. I will have to read over it a bit more before I understand it fully, although from the example you linked me to, this looks like the proper way I should be doing things here.
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    2. COI have read further into this, read the link you gave and links on that site. good resource. This is defiantly the answer I was after, although it did assume i understand what abstraction and interfaces were, which i didnt, but i guess that was a fair assumption.
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