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copied!<p>As the type of <code>args</code> is an <code>ArrayList<Object></code>, you're not avoiding the boxing anyway:</p> <pre><code>// This code... float v = (Float)elem.get(names[i]); arg.add(v); // Will actually be equivalent to: float v = (Float)elem.get(names[i]); Float boxed = v; arg.add(boxed); </code></pre> <p>If the point is to call a constructor by reflection, then you're going to <em>have</em> to pass in a <code>Float</code> for any <code>float</code> parameters - that's just how it works.</p> <p>So basically, change <code>float.class</code> to <code>Float.class</code> and it should all work fine. EDIT: Ah, except then the <code>par</code> list will have the wrong type. Basically you want to <em>cast</em> with <code>Float.class</code>, but <em>add</em> <code>float.class</code> to the list of parameter types.</p> <p>You probably want a map from primitive types to wrapper types, like this:</p> <pre><code>private static final Map<Class<?>>, Class<?>> PRIMITIVE_TYPE_MAP = buildPrimitiveTypeMap(); private static Map<Class<?>>, Class<?>> buildPrimitiveTypeMap() { Map<Class<?>>, Class<?>> map = new HashMap<Class<?>>, Class<?>>(); map.put(float.class, Float.class); map.put(double.class, Double.class); // etc return map; } </code></pre> <p>Then:</p> <pre><code>String names[] = { "x", "y", "src" }; Class types[] = { float.class, float.class, String.class }; for (int i = 0; i < names.length; i++) { if (elem.containsKey(names[i])) { par.add(types[i]); // For primitive types, only box to the wrapper type Class<?> castType = PRIMITIVE_TYPE_MAP.get(types[i]); if (castType == null) { castType = types[i]; } arg.add(castType.cast(elem.get(names[i]))); } } </code></pre> <hr> <p>In fact, if you trust that the values are of the right type already, I suspect you can just do:</p> <pre><code>arg.add(elem.get(names[i])); </code></pre> <p>After all, you're just casting to a particular type and then losing that type information again... using the <code>cast</code> call does perform a check that the execution-time types are correct though, so you may want to keep it for that reason.</p>

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