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POHow to iterate on a hashmap of generics?
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  1. POHow to iterate on a hashmap of generics?
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    copied!<p>I have an object model which have a parent, that I'll call here MyParent.java. This class have two sub-classes named MySub1.java and MySub2.java.</p> <p>I have two HashMaps, one containing MySub1 instances and the other containing MySub2 instances. I'm trying to do a piece of code that can handle both HashMaps and do exactly the same thing (later on, having MySub1 or MySub2 instances will have some effect, but not here).</p> <p>Here is the part of code that does compile : </p> <pre><code>HashMap&lt;String, ? extends MyParent&gt; map = null; if (some condition) map = // get a HashMap&lt;String, MySub1&gt; if (some other condition) map = // get a HashMap&lt;String, MySub2&gt; </code></pre> <p>But now, I cannot figure out how to iterate on the <code>map</code> variable. I need to do it through an iterator and not though an iteration over the elements of the <code>keySet()</code> because I will need to remove some of the elements from the hashmap.</p> <p>Here is the part of my code that does NOT compile : </p> <pre><code>if(map != null &amp;&amp; map.size() &gt; 0){ Iterator&lt;Entry&lt;String, ? extends MyParent&gt;&gt; i = map.entrySet().iterator(); while(i.hasNext()){ Map.Entry&lt;String, MyParent&gt; pair = (Map.Entry&lt;String, MyParent&gt;) i.next(); // get the object from the pair and handle it } } </code></pre> <p>Eclipse does print me this error message on the line where I do create the iterator : </p> <pre><code> cannot convert from Iterator&lt;Map.Entry&lt;String,capture#5-of ? extends MyParent&gt;&gt; to Iterator&lt;Map.Entry&lt;String,? extends MyParent&gt;&gt; </code></pre> <p>I really dont get the error message. If I change the first line of my code for :</p> <pre><code>HashMap&lt;String, MyParent&gt; map = null </code></pre> <p>Now the code that was not working does work, but the working code does not work anymore with this error message : </p> <pre><code>cannot convert from HashMap&lt;String,MySub1&gt; to HashMap&lt;String,MyParent&gt; </code></pre> <p>Any idea ?</p>
 

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