Question

I am trying to run a file from command line. The file is a .class file and is apart of a larger project that I compiled in Netbeans. I navigated to the .class file and ran

java MyFile

And I got:

Exception in thread "main" java.lang.NoClassDefFoundError: PersonTest/class
Caused by: java.lang.ClassNotFoundException: PersonTest.class
   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)

Could not find the main class: PersonTest.class. Program will exit

Whats up with that? (I should mention that i’m running ubuntu)

Answer 1

You need to check this useful link java – the Java application launcher:

By default, the first non-option
argument is the name of the class to
be invoked. A fully-qualified class
name should be used

So, you have to write the full qualified name of the class (this includes the package name).

So, the right way to execute your command is this (from the root dir where your class files are stored):

> java my.package.MyFile

Also, make sure to include all the needed dependencies at the classpath (-cp) argument (check the referenced link).

UPDATE: to include a classpath setting example:

java -classpath C:\MyProject\classes;C:\MyProject\lib\utility.jar my.package.MyFile

With this, the java runtime will search for the classes at the C:\MyProject\classes directory, and at the C:\MyProject\lib\utility.jar JAR file. You’ll need not only your class direct dependencies, but the dependencies needed by the referenced files (the whole tree).