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POHow can I call methods on items in a ReferenceQueue if type erasure has allowed me to only call Object() methods?
 

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  1. POHow can I call methods on items in a ReferenceQueue if type erasure has allowed me to only call Object() methods?
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    <p>I have a reference queue, declared as:</p> <pre><code>ReferenceQueue&lt;MapChunk&gt; rqueue = new ReferenceQueue&lt;&gt;(); </code></pre> <p>and I have some soft references constructed in the form of</p> <pre><code>SoftReference ref=new SoftReference&lt;MapChunk&gt;(ourChunk, rqueue); </code></pre> <p>As per the docs, <code>rqueue</code> is <code>ReferenceQueue&lt;? extends MapChunk&gt;</code></p> <p>I wish to call a handler on their garbage collection, which is why I put them into the queue. However, when I begin processing the queue from another thread, I retrieve the object from the queue via</p> <pre><code>Reference ref=rqueue.poll(); synchronized (chunks) { synchronized (MapDatabase.class) { chunks.put(ref.get().getPosition(), ref.get()); } } </code></pre> <p>My compiler errors indicate type erasure has occurred and I'm left with <code>ref.get()</code> being an object(due to the raw type of the queue). I can neither call methods on the object that I need nor can I pass it to a method that requires a <code>MapChunk</code> itself. Surely this impedes many uses of the reference queue, and I'm likely doing something wrong in that case. I am certain that I will only get <code>MapChunk</code> objects at runtime, so should I use a cast? Do something else? Not use the reference queue at all?</p> <p>Edit: If I use <code>Reference&lt;MapChunk&gt; ref=rqueue.poll()</code> I get the following:</p> <pre><code>cannot convert from Reference&lt;capture#1-of ? extends MapChunk&gt; to Reference&lt;MapChunk&gt; </code></pre> <p>When I use <code>Reference&lt;? extends MapChunk&gt; ref=rqueue.poll();</code> the error on that line is resolved, but another error comes up when I try to use <code>ref</code>:</p> <pre><code>The method addMapChunk(Position, SoftReference&lt;MapChunk&gt;) in the type HashMap&lt;Position,SoftReference&lt;MapChunk&gt;&gt; is not applicable for the arguments (Position, capture#3-of ? extends MapChunk). </code></pre> <p>Edit: I guess it was simply a buggy error message as the type did convert properly when another bug was fixed.</p>
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    1. USAndrey Akhmetov
    1. USAndrey Akhmetov
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