Strange class files appearing in my bin folder

Question

I am using Eclipse + Window Builder + few third party libraries to build a gui application,

Entry point for my application resides in MainWindow.java file, which also contains the gui of the application, other than that I have few helper classes.

My application works fine, but when I checked into bin folder I find four more class files there namely: 1. MainWindow$1.class 2. MainWindow$2.class 3. MainWindow$3.class 4. MainWindow$4.class.

Now I don't understand why these files are here, When I deleted these files, Eclipse throws an exception

Exception in thread "main" java.lang.NoClassDefFoundError: gui/MainWindow$1
at gui.MainWindow.main(MainWindow.java:71)
    Caused by: java.lang.ClassNotFoundException: gui.MainWindow$1
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)

the code that throws the exception is:

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                MainWindow window = new MainWindow();
                window.frmMailExtractor.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });

I am not able to find out why these files are there and who put them? any ideas?

OK so these are the anonymous classes, but why the Exception then?...and why can't I see them in my eclipse..becasue when I export it as a runnable jar, the jar throws the same exception

They refer to anonymous inner classes. See http://stackoverflow.com/questions/380406/java-inner-class-class-file-names — Bruno Lowagie, Sep 14 '12 at 10:12
So How would I add these in my jar..I need to run my application as a jar...When I create the jar using Eclipse's export option, It gives the same exception and closes. — Sudh, Sep 14 '12 at 10:18

Péter Török · Accepted Answer · 2012-09-14T10:15:29.593

3

These are class files generated for anonymous inner classes inside MainWindow. It probably contains a bunch of event listeners implemented as such.

Anonymous inner classes get compiled into separate class files with the name <OuterClass>$<nnn>.class, where <nnn> is a compiler-generated number.

edited Sep 14 '12 at 10:15

answered Sep 14 '12 at 10:10

Péter Török

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So How would I add these in my jar..I need to run my application as a jar...When I create the jar using Eclipse's export option, It gives the same exception and closes. – Sudh Sep 14 '12 at 10:18
1

@Sudh, just rebuild your app to regenerate the missing class files again, the jar builder should automatically include all. – Péter Török Sep 14 '12 at 12:14

score 1 · Answer 2 · answered Sep 14 '12 at 10:11

1

Those are what anonymous classes get compiled into. The number in the filename is the ordinal of the related anonymous class in the respective Java compilation unit.

answered Sep 14 '12 at 10:11

Alexander Pavlov

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Strange class files appearing in my bin folder

2 Answers2