Clojure proxy JComboBox and IDeref gives java.lang.VerifyError

Question

Somewhere in my code, I am doing this:

(proxy [JComboBox IDeref] []
  (deref [] (.getSelectedItem this)))

While this works fine on my machine, some users have reported the following problem:

java.lang.VerifyError: class ggo.igs.gui.widgets.proxy$javax.swing.JComboBox$IDeref$db53459f 
  overrides final method 1®­+1ú h.1®ˆû1ú h
  at java.lang.ClassLoader.defineClass1 (ClassLoader.java:-2)
    java.lang.ClassLoader.defineClass (ClassLoader.java:676)
    java.security.SecureClassLoader.defineClass (SecureClassLoader.java:124)
    java.net.URLClassLoader.defineClass (URLClassLoader.java:260)
    java.net.URLClassLoader.access$100 (URLClassLoader.java:56)
    java.net.URLClassLoader$1.run (URLClassLoader.java:195)
    java.security.AccessController.doPrivileged (AccessController.java:-2)
    java.net.URLClassLoader.findClass (URLClassLoader.java:188)
    com.sun.jnlp.JNLPClassLoader.findClass (JNLPClassLoader.java:332)
    java.lang.ClassLoader.loadClass (ClassLoader.java:317)
    java.lang.ClassLoader.loadClass (ClassLoader.java:252)
    java.lang.ClassLoader.loadClassInternal (ClassLoader.java:375)
    ggo.igs.gui.widgets$combo_box.doInvoke (widgets.clj:124)
    clojure.lang.RestFn.invoke (RestFn.java:440)

I don’t see where I could override the final method, especially not with this strange “name”. Any ideas what could be wrong?

Answer 1

I would start by checking the JDK version in both environments (your and your users): java.lang.VerifyError could be the result when you compiled against a different library than what you use at runtime.