I recently made some updates to my NetBeans development environment and encountered this weird error:

d:\dev\myproject\nbproject\build-impl.xml:485: The libs.CopyLibs.classpath property is not set up.
This property must point to
org-netbeans-modules-java-j2seproject-copylibstask.jar file which is part
of NetBeans IDE installation and is usually located at
/java/ant/extra folder.

Either open the project in the IDE and make sure CopyLibs library
exists or setup the property manually. For example like this:
ant -Dlibs.CopyLibs.classpath=a/path/to/org-netbeans-modules-java-j2seproject-copylibstask.jar

BUILD FAILED (total time: 0 seconds)

I was able to resolve it by following these steps:

  1. In NetBeans, select Tools > Options > Miscellaneous > Ant
  2. In the Properties section, add the following property


Click OK and Build your project again. This error will go away. Hope this helps. Happy coding!