java.lang.LinkageError when loading class from .zip file

Question

I'm trying to make a class loader that will load .class files inside a .zip file. I followed this tutorial (https://weblogs.java.net/blog/2008/07/25/how-load-classes-jar-or-zip), but when i run the program, i get this error:

java.lang.LinkageError: loader (instance of org/freeforums/geforce/genforcer/main/ZipClassLoader): attempted duplicate class definition for name: "test/TestClass"

The error comes from line 30, which is:

return defineClass(filename, out.toByteArray, 0, out.size());

I call the method by using:

zipClassLoaderObj.findClass("test.TestClass");

Does anyone know what i'm doing wrong?

Sorry, i'm brand new to using ClassLoader's and other semi-advanced features. Could you explain what that means? — Geforce132
– Geforce132, Commented Feb 27, 2014 at 19:05
What I'm asking has nothing to do with classloaders or much else. I'm asking if when you run the program the class is already on the classpath, loaded, etc. — Dave Newton
– Dave Newton, Commented Feb 27, 2014 at 19:08
Oh, yeah, it's loaded. I added the line from which the error originates from to the main post. — Geforce132
– Geforce132, Commented Feb 27, 2014 at 19:12
Subclasses of LinkageError indicate that a class has some dependency on another class; however, the latter class has incompatibly changed after the compilation of the former class. Although it's something of a "garbage" error. I suspect in this case you get it because you've already loaded a version of test/TestClass. — Hot Licks
– Hot Licks, Commented Feb 27, 2014 at 19:16

Geforce132 · Accepted Answer · 2014-02-27 19:53:25Z

1

Found the problem. I was calling the method two times because it was in a 'for' loop with a bunch of other code. Just took it out of the loop, and now it works perfectly. Don't know why i couldn't figure that out myself. Thanks for the help!

answered Feb 27, 2014 at 19:53

Geforce132

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