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    <p>The <a href="http://www.savarese.com/software/libssrckdtree-j/api/com/savarese/spatial/NearestNeighbors.html#get%28com.savarese.spatial.KDTree,%20P,%20int,%20boolean%29" rel="nofollow">api documentation for NearestNeighbor#get()</a> indicates that the method takes four arguments of types KDTree, P, int, boolean, which are all Java types.</p> <p>Your error message indicates that you passed in KDTree, RubyArray, RubyFixnum, RubyBoolean. So, KDTree looks ok. I believe JRuby will automatically coerce Fixnum and Boolean to the appropriate Java types. That leaves the second arg where you are passing RubyArray where the method expects P.</p> <p>The documentation of NearestNeighbors indicates that P is a generic type, <code>P extends Point&lt;Coord&gt;</code>. <code>Point</code> is an interface. <code>GenericPoint</code> implements that interface. So instead of passing <code>[1,1]</code>, try passing <code>Java::com.savarese.spatial.GenericPoint.new(1,1)</code></p> <p>edit:</p> <p>Looking a bit further, <code>GenericPoint</code> must be created with <code>Coord</code>, another generic type <code>Coord extends java.lang.Comparable&lt;? super Coord&gt;</code>. In Java, there are two kinds of ints, the primitive type <code>int</code> (fast), and the "boxed" object <code>java.lang.Integer</code>. <code>Integer</code> implements the <code>Comparable</code> interface, which is required by <code>GenericPoint</code>. I did not get any errors running the following:</p> <pre><code>require 'java' require 'libssrckdtree-j-1.0.2.jar' GenericPoint = Java::com.savarese.spatial.GenericPoint KDTree = Java::com.savarese.spatial.KDTree NearestNeighbors = Java::com.savarese.spatial.NearestNeighbors def box(i) java.lang.Integer.new(i) end tree = KDTree.new def generate_points(tree, size) size.times do x = box(rand(100)) y = box(rand(100)) point = GenericPoint.new(x, y) tree.put(point, point.to_s) end end generate_points(tree, 20000) nearest = NearestNeighbors.new() point = GenericPoint.new(box(1), box(1)) nearest.get(tree, point, 1, false) </code></pre> <p>A note about the above, normally in Java to create a boxed <code>Integer</code>, one uses <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Integer.html#valueOf%28int%29" rel="nofollow"><code>java.lang.Integer.valueOf(int)</code></a>. For reasons beyond me, this resulted in the same error one gets when using <code>int</code>: <code>NativeException: java.lang.ClassCastException: org.jruby.RubyFixnum cannot be cast to java.lang.Number</code>. So I instead used the constructor, <code>java.lang.Integer.new</code>.</p>
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    1. POjruby adding a java library
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    1. USPatrick
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    1. COthanks - however it is erroring on the get - not the arguments? when i change to a generic point it is still doing the same
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      1. USCharlie Davies
    2. CO+1. Nice answer!
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      1. USMichelle Tilley
 

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