Hello!

I just now got into java and seemed of gotten stuck before I could even get started.

I went through a basic "Hello World" tutorial but I can’t seem to run the program. When I run it from the command prompt I get a NoClassDefFoundError. I have tried to unset the java class with the command “unset CLASSPATH” but I keep getting the same error. Any ideas? I’m sure its an easy fix.

Here is what I have tried:

sean@CrunchBang:~/java$ dir
HelloWorldApp.class HelloWorld.java
sean@CrunchBang:~/java$ CLASSPATH=/home/sean/java
sean@CrunchBang:~/java$ echo $CLASSPATH
/home/sean/java
sean@CrunchBang:~/java$ dir
HelloWorldApp.class HelloWorld.java
sean@CrunchBang:~/java$ java HellowWorld.java
Exception in thread "main" java.lang.NoClassDefFoundError: HellowWorld/java
Caused by: java.lang.ClassNotFoundException: HellowWorld.java
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:334)
Could not find the main class: HellowWorld.java. Program will exit.
sean@CrunchBang:~/java$

Thanks

Hi,

Check your code to see if you misspelled anything.

"Could not find the main class: HellowWorld.java. Program will exit."

Ha, oops. I wish that was the problem but here is the error I'm getting:

sean@CrunchBang:~$ CLASSPATH=/home/sean/java
sean@CrunchBang:~$ echo $CLASSPATH
/home/sean/java
sean@CrunchBang:~$ cd java
sean@CrunchBang:~/java$ dir
HelloWorldApp.class HelloWorld.java
sean@CrunchBang:~/java$ java HelloWorld.java
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld/java
Caused by: java.lang.ClassNotFoundException: HelloWorld.java
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:334)
Could not find the main class: HelloWorld.java. Program will exit.
sean@CrunchBang:~/java$ dir
HelloWorldApp.class HelloWorld.java
sean@CrunchBang:~/java$

Did you mean to run the following?

$ javac HelloWorld.java

then run

$ java HelloWorld

I did, I believe this is when the .class file is generated. I'm not sure why it's not finding it when the program is run:


sean@CrunchBang:~/java$ javac HelloWorld.java
sean@CrunchBang:~/java$ java HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld
Caused by: java.lang.ClassNotFoundException: HelloWorld
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:334)
Could not find the main class: HelloWorld. Program will exit.
sean@CrunchBang:~/java$

In your first post
the class has a different name.

Try again, compiling from scratch, and don't bother with the CLASSPATH variable - it will look in the current directory automatically.

If it still fails, post your .java code.

Please use [code][/code] tags for all code and command output.

1 members found this post helpful.

Awesome! After restarting from scratch and recompiling the code, it worked! Thanks for everyone's help.

sean@CrunchBang:~/java$ dir
HelloWorld.java
sean@CrunchBang:~/java$ javac HelloWorld.java
sean@CrunchBang:~/java$ dir
HelloWorld.class HelloWorld.java
sean@CrunchBang:~/java$ java HelloWorld
Hello, World