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POJava SortedMap to Scala TreeMap
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  1. POJava SortedMap to Scala TreeMap
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    copied!<p>I'm having trouble converting a java SortedMap into a scala TreeMap. The SortedMap comes from deserialization and needs to be converted into a scala structure before being used. </p> <p>Some background, for the curious, is that the serialized structure is written through XStream and on desializing I register a converter that says anything that can be assigned to <code>SortedMap[Comparable[_],_]</code> should be given to me. So my convert method gets called and is given an <code>Object</code> that I can safely cast because I know it's of type <code>SortedMap[Comparable[_],_]</code>. That's where it gets interesting. Here's some sample code that might help explain it.</p> <pre><code>// a conversion from comparable to ordering scala&gt; implicit def comparable2ordering[A &lt;: Comparable[A]](x: A): Ordering[A] = new Ordering[A] { | def compare(x: A, y: A) = x.compareTo(y) | } comparable2ordering: [A &lt;: java.lang.Comparable[A]](x: A)Ordering[A] // jm is how I see the map in the converter. Just as an object. I know the key // is of type Comparable[_] scala&gt; val jm : Object = new java.util.TreeMap[Comparable[_], String]() jm: java.lang.Object = {} // It's safe to cast as the converter only gets called for SortedMap[Comparable[_],_] scala&gt; val b = jm.asInstanceOf[java.util.SortedMap[Comparable[_],_]] b: java.util.SortedMap[java.lang.Comparable[_], _] = {} // Now I want to convert this to a tree map scala&gt; collection.immutable.TreeMap() ++ (for(k &lt;- b.keySet) yield { (k, b.get(k)) }) &lt;console&gt;:15: error: diverging implicit expansion for type Ordering[A] starting with method Tuple9 in object Ordering collection.immutable.TreeMap() ++ (for(k &lt;- b.keySet) yield { (k, b.get(k)) }) </code></pre>
 

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