Eclipse plugin development: How to include another project?-Collection of common programming errors

I’m developing a Eclipse plugin. From this plugin I want to instantiate classes from another project that I have developed. I added this project to the build path, but nevertheless, I get the following error:

Caused by: java.lang.ClassNotFoundException: myPackage.myClass
    at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(
    at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 38 more

I’m sure that I have to add the refernce to this project somewere else, but where? Any hints?

Originally posted 2013-11-09 23:05:38.