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POJava classloading running extremely slow?
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  1. POJava classloading running extremely slow?
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    copied!<p>I'm trying to load a java .class file dynamically and call it by reflection.</p> <p>I've got a class called Foo; it has an empty constructor and has one method called doit() which takes a String argument and returns a String. Also it reverses the String.</p> <p>Here is my code:</p> <pre><code> URL url = new URL("file://C:/jtest/"); URLClassLoader loader = new URLClassLoader(new URL[]{url}); Class&lt;?&gt; cl = loader.loadClass("Foo"); Constructor&lt;?&gt; cons = cl.getConstructor((Class[])null); Object ins = cons.newInstance(new Object[]{}); Method meth = cl.getDeclaredMethod("doit", String.class); Object ret = meth.invoke(ins, new Object[]{"!dlroW olleH"}); System.out.println((String)ret); </code></pre> <p>As expected this prints "Hello World!". However, it takes about <b>30 seconds</b> to complete. I know reflection is slow, but I expect it to be 10 ms or something.</p> <p>I'm using Eclipse with JRE 1.6.0_13, and I'm running Windows Vista.</p> <p>What am I doing wrong here?</p> <p>Thanks.</p> <p><b>Edit:</b> I've profiled the code, and all of its time is used in the third line(loadClass()). Everything else happens instantly.</p> <p><b>Edit:</b> I've put the code in a loop; the slow function somehow gets optimized and takes 30 seconds only on the first loop.</p> <p><b>Edit:</b> I've found the solution.</p> <p>Instead of: </p> <p><code>URL url = new URL("file://C:/jtest/");</code></p> <p>I changed it to:</p> <p><code>URL url = new URL("file:/C:/jtest/");</code></p> <p>Now it works perfectly. I don't know why it works, but I don't see how I (and 5 other people) could have missed that. Now I feel dumb..</p>
 

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