ClassNotFoundException - only for one class file, but others OK

[Gordy.Liang]

This is for an old java application I developed long long time ago. A bunch of .class files have been built since then and I am sure they worked very well.

Now when I re-open this application, it prompts ClassNotFoundException like following (note that I have set CLASSPATH correctly):

D:\simulation.exe.applet>java Simulation
Exception in thread "main" java.lang.NoClassDefFoundError: netscape/javascript/J
SObject
at Simulation.<init>(Simulation.java:17)
at Simulation.main(Simulation.java:57)
Caused by: java.lang.ClassNotFoundException: netscape.javascript.JSObject
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)
... 2 more
It looks like the problem is that when the constructor call "new simPanel(...)", the class is not found.

If I try below, it also shows that the class of simPanel can not be found:
D:\simulation.exe.applet>java simPanel
Exception in thread "main" java.lang.NoClassDefFoundError: netscape/javascript/J
SObject
Caused by: java.lang.ClassNotFoundException: netscape.javascript.JSObject
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)
Could not find the main class: simPanel. Program will exit.

But the interesting is that, I have bunch of other classes in the same directory, and if I try to launch those classes, they all can be loaded correctly :confused: (just prompting no main function defined as they are not the main class):

D:\simulation.exe.applet>java simApplet
Exception in thread "main" java.lang.NoSuchMethodError: main

[Hibernate]

Seems like you classes have class and instance initializers:

class ClassName
{
    static
    {
        //Code that runs as soon as possible when a the class is access for
        //the first the, usually for assigning static variables with values created
        //with multiple instructions.
    }
    

    {
        //Code that runs directly after construction.
    }
}

Note that

class ClassName
{
    static AnotherClass variable0 = new AnotherClass(); //This is probably why your code runs.
    AnotherClass variable1 = new AnotherClass();
}

is basically the same thing.

[Gordy.Liang]

Yes it is similar to the codes above.

Exactly, the code in probmem is:

Simulation.java
public class Simulation extends Frame
{
...
public Simulation()
{
...
sp=new simPanel(this);
...

static public void main(String args[])
{
new Simulation().show();
}
...
}
simPanel.java
public class simPanel extends Panel
{
...
}

All the class has been compiled and .class files are there. The problem is that it is prompted that the class file simPanel.class can not be found...

[Gordy.Liang]

Ah yes, I gonna to understand and have resolved the issue now.

The error message below indicates the class not found for "netscape/javascript/JSObject", but not the class of simPanel. Actually the class simPanel imports JSObject, that why it fails when loading simPanel. I remember that I do have used JSObject if the program runs as an Applet.

Exception in thread "main" java.lang.NoClassDefFoundError: netscape/javascript/J
SObject
at Simulation.<init>(Simulation.java:17)
at Simulation.main(Simulation.java:57)
Caused by: java.lang.ClassNotFoundException: netscape.javascript.JSObject
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)
... 2 more

To resolve the probjem I added following path to CLASSPATH environment variable and it works now.

C:\Program Files\Java\jre6\lib\plugin.jar

[Hibernate]

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