cannot execute a java class java.lang.NoClassDefFoundError:

Question

i'm new to java. i've created a file called HelloWorld.java;

package tp;

 /**
 *
 * @author Utilisateur
 */
    public class HelloWorld {
        public static void main(String[] args) {
            System.out.println("HelloWorld works!");
    }
}

compiled it by executing the command: javac HelloWorld.java in the same folder as HelloWorld.java is in; executed the code by doing: java -cp . HelloWorld in the same folder as HelloWorld.java is in.

but i get this error message

Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong nam
e: javaTp/HelloWorld)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    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)
    at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

can anyone help?

jacksonps4 · Accepted Answer · 2014-01-23 21:43:53Z

2

The package name is your issue.

Java uses directories in compiled class folders to denote packages. Hence as your HelloWorld class defines itself as being in package 'tp', you need to do one of the following:

You can either run this (with your existing class):

> java -cp . tp.HelloWorld

Or you can remove the package declaration from the top of your class, recompile and run:

> java -cp . HelloWorld

answered Jan 23, 2014 at 21:43

jacksonps4

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1 Comment

Albee Over a year ago

Thanks for answer. choosed the second solution. it works now!

Peter Bratton · Accepted Answer · 2014-01-23 21:40:35Z

1

Because you declared the package tp, Java expects your HelloWorld.class file to live in a directory ./tp.

Typically a Java project will have a nested directory structure compiled to a mirrored one, such as:

src/
  tp/
    HelloWorld.java
classes/
  tp/
    HelloWorld.class

answered Jan 23, 2014 at 21:40

Peter Bratton

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Comments

Sujith Surendranathan · Accepted Answer · 2014-01-23 21:39:17Z

0

You need to use the full name: java tp.HelloWorld

answered Jan 23, 2014 at 21:39

Sujith Surendranathan

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2 Comments

64BitBob Over a year ago

Try again. His package name is "tp". It's also likely that he does not have the correct folder structure in place.

Sujith Surendranathan Over a year ago

Space in between. Edited.

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