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POAPI java 5 and more: should I return an array or a Collection?
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  1. POAPI java 5 and more: should I return an array or a Collection?
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    copied!<p>In the spirit of <a href="https://stackoverflow.com/questions/171156/best-practices-always-return-a-never-a">Best Practices: Always return a ____, never a ____</a>, I face a similar question in my upcoming <a href="https://stackoverflow.com/questions/219164/generics-in-legacy-code">migration from JDK1.4.2 to JDK5 and more</a>. (Yes, I <em>know</em>, <a href="http://java.sun.com/products/archive/eol.policy.html" rel="nofollow noreferrer">JDK1.4.2 is EOL!</a> ;-) ).</p> <p>For functions returning a collection (which are not simple <a href="https://stackoverflow.com/questions/35007/how-to-expose-a-collection-property">property collections</a>), I always prefer (in JDK1.4.2) returning an Array instead of a generic List, because:</p> <ul> <li>it enforces the returning type (<code>MyObject[]</code> instead of List of Objects, much more <strong><em>type-safe</em></strong> on a static -- as in 'compilation' -- level)</li> <li>it <em>suggests</em> a 'read-only' character to the returned collection (it is more complicated to add an element to the collection, even though this is not as rigorous as the 'read-only' keyword in c#). This is not the same as saying it is 'immutable' since the references inside the array can still be modified...</li> </ul> <p>Of course, I do always <em>create</em> this returned array (I do not expose any 'internal' array)</p> <p>Now, In JDK5 and more, I could use <code>List&lt;MyObject&gt;</code> if I want to. </p> <p><strong>What are the good reasons for choosing to return <code>MyObject[]</code> instead of List or <code>Collection&lt;MyObject&gt;</code> when coding in java5 ?</strong></p> <p>Bonus, if <code>Collection&lt;MyObject&gt;</code> is used, is it possible to:</p> <ul> <li>enforce a read-only attribute on the returned collection ? (no <code>add()</code> or <code>remove()</code> possible)</li> <li>enforce an immutable aspect to the returned collection ? (even the references of that collection can not be modified)</li> </ul> <p>PS: The <a href="http://www.angelikalanger.com/GenericsFAQ/JavaGenericsFAQ.html" rel="nofollow noreferrer">JavaGenericFAQ</a> did not quite have that one.</p>
 

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