ClassNotFoundException when running in Command Prompt

Question

I am very new to java and tried to run a simple code of calculating volume. The code is below:

package chapter6;

class Box {

    double width;
    double height;
    double depth;
}

package chapter6;

    public class BoxDemo {

        public static void main(String[] args) {

            Box myBox = new Box();
            double vol;

            myBox.depth = 1;
            myBox.height = 2;
            myBox.width = 3;

            vol = myBox.depth * myBox.height * myBox.width ;        

            System.out.println("Volume: " + vol);
        }

    }

I am able to run the code from eclipse, but when i try to run the code in Command Prompt i get the error:

C:\Prabhjot\Java\CompleteRefence\build\classes>java BoxDemo.class
Exception in thread "main" java.lang.NoClassDefFoundError: BoxDemo/class
Caused by: java.lang.ClassNotFoundException: BoxDemo.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: BoxDemo.class.  Program will exit.

Please assist.

Jops · Accepted Answer · 2013-04-27 06:31:47Z

14

First class file should be at this location:

C:\Prabhjot\Java\CompleteRefence\build\classes\chapter6\BoxDemo.class

Then you should be inside:

C:\Prabhjot\Java\CompleteRefence\build\classes>

Then issue the command:

java chapter6.BoxDemo

enter image description here

edited Apr 27, 2013 at 6:31

answered Apr 27, 2013 at 6:16

Jops

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Comments

NilsH · Accepted Answer · 2013-04-27 06:16:24Z

4

You have put your class in a package called chapter6. This means that the java file should be in a folder called chapter6 in the class root folder of your project. And when you run it, you should be in the root folder and use the command java chapter6.BoxDemo

answered Apr 27, 2013 at 6:16

NilsH

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1 Comment

prabh Over a year ago

thanks, now i got it. I was doing a mistake of using the command from C:\Prabhjot\Java\CompleteRefence\build\classes\chapter6 which shaould have been the way u mentioned. thanks!!

gprathour · Accepted Answer · 2013-04-27 06:25:13Z

2

There is mistake in how you are running your program from console.

You are doing

java BoxDemo.class

But you need to do only

java BoxDemo

While running your program you don't need to mention .class with the name.

and if you are accessing it from root folder then you need to do

java chapter6.BoxDemo

answered Apr 27, 2013 at 6:25

gprathour

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Comments

samba · Accepted Answer · 2013-04-27 06:31:34Z

1

try this

C:\Prabhjot\Java\CompleteRefence\build\classes>java chapter6.BoxDemo (RUN)

There is no need to specify .class extinction to the file while running.After compiling the java file it will create the .class file.

EXAMPLE

edited Apr 27, 2013 at 6:31

answered Apr 27, 2013 at 6:11

samba

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3 Comments

prabh Over a year ago

the problem above is my code is in package, pls see: package chapter6;

NilsH Over a year ago

No need for the -d in this example, and your package name is "wrong", but other than that, it's correct now.

NilsH Over a year ago

Great! I'm not able to undo the vote though, because both my comments crossed your edits...

user1131435 · Accepted Answer · 2013-04-27 06:14:12Z

0

When you invoke BoxDemo.class, Java looks for a class called class in the BoxDemo package, which doesn't exist. As you can see from the output java.lang.NoClassDefFoundError: BoxDemo/class, it's searching for a directory BoxDemo.

Instead, just specify the class name: BoxDemo; e.g. java BoxDemo.

answered Apr 27, 2013 at 6:14

user1131435

2 Comments

user1131435 Over a year ago

I'm not sure why this was downvoted, as this provides the exact same answer as above, just with more info.

NilsH Over a year ago

I didn't downvote, but your example won't work, since the package name is not correct.

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