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Thread: Main Class Not Found Problem

  1. #1
    Junior Member
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    Default Main Class Not Found Problem

    Hello. I haven't done much Java programming for a few years and have recently installed the Java 6 SDK. I cant seem to figure out how to fix this problem though. It works fine under Java 5. Here is the error.
    C:\Program Files\Java\jdk1.6.0_16\bin>java "z:\java_stuff\SwingExample.class"
    Exception in thread "main" java.lang.NoClassDefFoundError: z:\java_stuff\SwingEx
    Caused by: java.lang.ClassNotFoundException: z:\java_stuff\SwingExample.class
            at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
            at java.security.AccessController.doPrivileged(Native Method)
            at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
            at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
            at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
    Could not find the main class: z:\java_stuff\SwingExample.class.  Program will e

    Here is the actual Java code. Just a simple JFrame example.
    import java.awt.*; 
    import javax.swing.*;
     * Basic Swing example.
    public class SwingExample {
        public static void main(String[] args) {
            // Create a JFrame, which is a Window with "decorations", 
            // i.e. title, border and close-button
            JFrame f = new JFrame("Swing Example Window");
            // Set a simple Layout Manager that arranges the Components
            f.setLayout(new FlowLayout());
            // Add a label
            f.add(new JLabel("Hello world!"));
            // "Pack" the window, making it "just big enough".
            // Set the default close operation for the window, 
            // or else the program won't exit when clicking close button
            // Set the visibility as true, thereby displaying it

    Any insight would be greatly appreciated. Thank you.

    Edit: Forgot to mention but it compiles just fine and the class and filename match.

    Edit: Finally found the problem.
    Last edited by shadow; September 28th, 2009 at 08:02 PM.

  2. #2
    Super Moderator Json's Avatar
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    Default Re: Main Class Not Found Problem

    Please mark as solved

    // Json

  3. #3
    mmm.. coffee JavaPF's Avatar
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    Default Re: Main Class Not Found Problem

    Hello shadow,

    Welcome to the Java Programming Forums.

    What was the solution?
    Please use [highlight=Java] code [/highlight] tags when posting your code.
    Forum Tip: Add to peoples reputation by clicking the button on their useful posts.

  4. #4
    Junior Member
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    Sep 2009
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    Default Re: Main Class Not Found Problem

    The classpath needed to be set. It's been so long since I've worked on anything non-PHP I forgot to set the environment variable. Now that I think of it, I believe I might have had my files on the same drive partition as java before so that is probably why it wasn't an issue before.

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