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copied!<p>You are implementing the <a href="http://en.wikipedia.org/wiki/Lazy_initialization" rel="noreferrer"><em>lazy initialization</em></a> pattern - where the instance is created when first used.</p> <p>But there is a simple trick that allows you to code a threadsafe implementation that <em>doesn't</em> require synchronization! It is known as the <a href="http://en.wikipedia.org/wiki/Initialization-on-demand_holder_idiom" rel="noreferrer"><em>Initialization-on-demand holder idiom</em></a>, and it looks like this:</p> <pre><code>public class CassandraAstyanaxConnection { private CassandraAstyanaxConnection(){ } private static class Holder { private static final CassandraAstyanaxConnection INSTANCE = new CassandraAstyanaxConnection(); } public static CassandraAstyanaxConnection getInstance() { return Holder.INSTANCE; } // rest of class omitted } </code></pre> <p>This code initializes the instance on the first calling of <code>getInstance()</code>, and importantly doesn't need synchronization because of the contract of the class loader:</p> <ul> <li>the class loader loads classes when they are first accessed (in this case <code>Holder</code>'s only access is within the <code>getInstance()</code> method)</li> <li>when a class is loaded, and before anyone can use it, all static initializers are guaranteed to be executed (that's when <code>Holder</code>'s static block fires)</li> <li>the class loader has its own synchronization built right in that make the above two points guaranteed to be threadsafe</li> </ul> <p>It's a neat little trick that I use whenever I need lazy initialization. You also get the bonus of a <code>final</code> instance, even though it's created lazily. Also note how clean and simple the code is.</p> <p><strong>Edit:</strong> You should set all constructors as private or protected. Setting and empty private constructor will do the work</p>

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