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copied!<p>The <code><?></code> syntax is java's way to specifying that the generic type is "unbounded" - ie it can be "anything". </p> <p><code>Enumeration<?></code> is an Enumeration with an "unbounded type" - you can assign an Enumeration of any type to such a variable, for example:</p> <pre><code>Vector<String> v = new Vector<String>(); Enumeration<String> es = v.elements(); Enumeration<?> e = es; // This assignment compiles OK </code></pre> <p>However, being unbounded, the nextElement() method of an <code>Enumeration<?></code> with return type <code>Object</code> (even if it's actually an <code>Enumeration<String></code>), so you'll may have to cast:</p> <pre><code>String s = (String)e.nextElement(); // Unsafe cast - compiler warning </code></pre> <p><br/> For background, <a href="http://download.oracle.com/javase/6/docs/api/java/util/Enumeration.html" rel="nofollow">Enumeration</a> is a typed interface with two methods <a href="http://download.oracle.com/javase/6/docs/api/java/util/Enumeration.html#hasMoreElements%28%29" rel="nofollow">hasMoreElements()</a> and <a href="http://download.oracle.com/javase/6/docs/api/java/util/Enumeration.html#nextElement%28%29" rel="nofollow">nextElement()</a>. It was an early (poor) attempt that was superseded by <a href="http://download.oracle.com/javase/6/docs/api/java/lang/Iterable.html" rel="nofollow">Iterable</a> and <a href="http://download.oracle.com/javase/6/docs/api/java/util/Iterator.html" rel="nofollow">Iterator</a>. A few old class use it, like <a href="http://download.oracle.com/javase/6/docs/api/java/util/Vector.html" rel="nofollow">Vector</a> and <a href="http://download.oracle.com/javase/6/docs/api/java/util/StringTokenizer.html" rel="nofollow">StringTokenizer</a>.</p>

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