java.lang.NoClassDefFoundError: (wrong name )

Question

I have run the application to load a class name called ChocolateMilk.java inside the netbeans project, I want to call this class using JFileChooser and then load it using ClassLoader.

here is the code for the method to get filename which is inside main class.

public static String getTheFileName() {
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (Exception ex) {
            System.err.println("Error " + ex.getMessage());
        }
        JFileChooser jfc = new  JFileChooser();
        jfc.setFileSelectionMode(fc.FILES_ONLY);
        jfc.setCurrentDirectory(new File(System.getProperty("user.dir") + File.separator + "build"+ File.separator + "classes"));
        jfc.showOpenDialog(null);
        File myfile ;

String fileNameWithOutExt = jfc.getName((myfile = jfc.getSelectedFile()));
        int pos = fileNameWithOutExt.lastIndexOf(".");
        if (pos > 0) {
            fileNameWithOutExt = fileNameWithOutExt.substring(0, pos);
        }
FilenameUtils.removeExtension(jfc.getName((myfile = jfc.getSelectedFile())));

        System.out.println("the program name is " +fileNameWithOutExt);
        return fileNameWithOutExt;
 }

I am calling getTheFileName method as a parameter for method called run inside foodProcessorEnvironmentA Class.

foodProcessorEnvironmentA.run(getTheFileName());

Here is the full code for the run method.

public void run(String programName) {
                URLClassLoader classLoader ;
    // the class path is a string that inside foodProcessorEnvironmentA class as URL instance variable 


  classLoader = new URLClassLoader(classPath);
            Class prgramClass = null;

            try {
                prgramClass = classLoader.loadClass(programName);
            } catch (ClassNotFoundException ex) {
                Logger.getLogger(FoodProcessorEnvironmentA.class.getName()).log(Level.SEVERE, null, ex);
            }
            AbstractFoodProcessorProgram program = null;
            try {
                program = (AbstractFoodProcessorProgram) prgramClass.newInstance();
            } catch (InstantiationException ex) {
                Logger.getLogger(FoodProcessorEnvironmentA.class.getName()).log(Level.SEVERE, null, ex);
            } catch (IllegalAccessException ex) {
                Logger.getLogger(FoodProcessorEnvironmentA.class.getName()).log(Level.SEVERE, null, ex);
            }

            program.setEnvironment(this);

            program.start();

    //        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        }

==========================

this is the output after running the project.

=============================

The fileName is: file:/Users/****/Desktop/FoodProcessor/build/classes/foodprocessor/
the program name is ChocolateMilk
Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: ChocolateMilk (wrong name: foodprocessor/ChocolateMilk)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:455)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:367)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at foodprocessor.FoodProcessorEnvironmentA.run(FoodProcessorEnvironmentA.java:31)
    at foodprocessor.FoodProcessor$1.run(FoodProcessor.java:191)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
    at java.awt.EventQueue.access$400(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:697)
    at java.awt.EventQueue$3.run(EventQueue.java:691)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

===========

I hope my question is clear. Thank you.

user207421 · Answer 1 · 2015-03-25T22:49:37.010

2

You have to provide the filename to Class.forName() in a form that corresponds to the fully-qualified class name including the package. In this case, foodprocessor.ChocolateMilk. You would need to know where the head of the package structure is in the file system; use that as the URL provided to the URLClassLoader; and then call loadClass("foodprocessor.ChocolateMilk").

edited Mar 25 '15 at 22:49

answered Mar 25 '15 at 22:37

user207421

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I know this is the easy way to do it, but I have another class other than ChocolateMilk, that's why I am using JFileChooser. I have to use JFileChooser. thanks EJP for your answer. – miss h Mar 25 '15 at 23:09

score 0 · Answer 2 · answered Mar 26 '15 at 14:57

0

I solved the problem by having a concatenation of a string of the package name with the dot and the programName variable.

here

prgramClass = classLoader.loadClass("foodprocessor."+programName);

That's it!

answered Mar 26 '15 at 14:57

miss h

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2
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java.lang.NoClassDefFoundError: (wrong name )

Here is the full code for the run method.

2 Answers2