Question

i’m kind of new to java. I use eclipse and i imported some jar files with some classes by going to properties -> Add External Jars;
The problem is that when i try to use a class from the jar i get the following exception:


Exception in thread "main" java.lang.NoClassDefFoundError: nextapp/echo2/app/event/ActionListener
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$000(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 java.lang.ClassLoader.loadClassInternal(Unknown Source)
at Program.main(Program.java:12)
Caused by: java.lang.ClassNotFoundException: nextapp.echo2.app.event.ActionListener
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 java.lang.ClassLoader.loadClassInternal(Unknown Source)
... 13 more


The class is supposed to create a window,
i guess that the jar has to import somehow other stuff or something like that,
How can i fix this?

PS. Sorry for the bad code , i don’t know tags here.

thansk,
Raxvan

Answer 1

Most jars you download will include 0-5 other jars that are needed. They all need included in order to use the jar. Very quickly you end up with 20 jars in a simple 1000 line Java project, but thems are the breaks.

Look inside your downloaded jar zip. Should be a lib directory or such with all the libs you need.