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POConstruction of a singleton class
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  1. POConstruction of a singleton class
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    copied!<p>An ethical question here. </p> <p>I'm planning on using several manager classes in my new project that will be performing various tasks across the whole project. These classes are singletons, but require construction based on parameters.</p> <p>As to when/where this construction has to happen, I have mixed feelings. I have these options so far:</p> <p><strong>Option A</strong></p> <p>It's easy to just pass these parameters to the <code>getInstance</code> method while having a default <code>null</code> value. On the very first call the parameters will be used, and any additional calls completely ignore them. </p> <p>While this works, doing so feels rather unlogical, for the following reasons:</p> <ul> <li><p><strong>It makes documentation unclear.</strong> <code>getInstance</code>' first parameter must be of type <code>Collection</code>, but can be <code>null</code>... what's going on here? You can argue that writing a line about this in the description will clear it up, but I'd prefer clarification to be unneccesary.</p></li> <li><p><strong>It feels faulty to pass <code>getInstance</code> any construction parameters.</strong> This is due to the fact that the method name does not explicity hint towards construction, making it unclear it will happen.</p></li> </ul> <p><strong>Option B</strong></p> <p>I'm thinking about a <code>setup</code> method. This method takes all parameters, calls the class constructor, and changes the internal class state to <code>initialized</code>. </p> <p>When calling the <code>getInstance</code> method prior to <code>setup</code>, it will throw a <code>NotInitializedException</code>. After setup has been called, any additional calls to <code>setup</code> will result in a <code>PreviouslyInitializedException</code>.</p> <p>After <code>setup</code> has been called, <code>getInstance</code> becomes available.</p> <p>Personally, this option appeals more to me. But it feels excessive.</p> <p>What option do you prefer? And why?</p>
 

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