WeakReference symbol cannot be found
<p>Already import the weakreference but the compiler cannot find the symbol, what wrong? There a memory leak in DumpReceiver.java I thought weakreference might free after used?</p>

<pre><code>import java.lang.ref.WeakReference;

Receiver r = new DumpReceiver(System.out);
WeakReference&lt;Receiver&gt; wr = new WeakReference&lt;DumpReceiver&gt;(r);


MidiInDump.java:64: cannot find symbol
symbol  : constructor WeakReference(javax.sound.midi.Receiver)
location: class java.lang.ref.WeakReference&lt;DumpReceiver&gt;
                WeakReference&lt;Receiver&gt; wr = new WeakReference&lt;DumpReceiver&gt;(r);

                                             ^
</code></pre>
