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    <p>Generics and arrays don't mix, basically. The short answer is that you can work around this problem. The longer answer is that you probably shouldn't and I'll explain why.</p> <p>You could use <a href="http://download.oracle.com/javase/6/docs/api/java/lang/reflect/Array.html#newInstance(java.lang.Class,%20int...)" rel="nofollow noreferrer"><code>Array.newInstance()</code></a> like this:</p> <pre><code>private Comparable[] hashtable; ... hashtable = (Comparable[])Array.newInstance(Comparable.class, tableSize); </code></pre> <p>but you <strong>can't</strong> create an array of your parameterized type.</p> <p>Arrays are <em>covariant</em>. That means they retain the type of their elements at runtime. Java's generics are not. They use <em>type erasure</em> to basically mask the implicit casting that is going on. It's important to understand that.</p> <p>So when you create an Object array you can't cast it to, say, a Comparable array (or any other type) because that is not correct.</p> <p>To give you an example. With generics this is perfectly legal:</p> <pre><code>List&lt;String&gt; list = new ArrayList&lt;String&gt;(); List&lt;Integer&gt; list2 = (List&lt;Integer&gt;)list; list.add(3); </code></pre> <p>It's also why you can't do this:</p> <pre><code>public &lt;T&gt; T newInstance(T t) { return new T(); // error! } </code></pre> <p>ie at runtime there is no knowledge of T's class. This is why the above code is more often written as:</p> <pre><code>public &lt;T&gt; T newInstance(T t, Class&lt;T&gt; clazz) { return clazz.newInstance(); } </code></pre> <p>because their is no runtime type for the generic argument. But with arrays:</p> <pre><code>String arr[] = new String[10]; Integer arr2[] = (Integer[])arr; // error! </code></pre> <p>What you should be doing in this case (imho) is not using arrays but using an <code>ArrayList</code>. In all honesty, there is very little reason to use arrays over an <code>ArrayList</code> and generics is just one example of that.</p> <p>For a better and more complete explanation see the (excellent) <a href="http://www.angelikalanger.com/GenericsFAQ/FAQSections/ParameterizedTypes.html#FAQ104" rel="nofollow noreferrer">Java Generics FAQ</a>:</p> <blockquote> <h2>Can I create an array whose component type is a concrete parameterized type?</h2> <p><strong><em>No, because it is not type-safe.</em></strong></p> <p>Arrays are covariant, which means that an array of supertype references is a supertype of an array of subtype references. That is, <code>Object[]</code> is a supertype of <code>String[]</code> and a string array can be accessed through a reference variable of type <code>Object[]</code>. </p> <p>...</p> </blockquote>
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    1. POGeneric arrays in Java
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    1. COdownvote - see answers using java.lang.reflect.Array.newInstance
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    2. COThank you very much! This is a great explanation that was more convoluted in other places on the web. Thanks!
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    3. CO`(Comparable[])Array.newInstance(Comparable.class, tableSize)` has the *exact* same effect as `new Comparable[tableSize]`
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