I'm wondering whether you have added the line System.loadLibrary(Core.NATIVE_LIBRARY_NAME); in the main method or not since it was one of the reasons why our very first example of openCV (the one that we did in class last week trying to load an image) didn't work.
Also, take a look at your "import" code because I think what should be included in Main.java, for example, is import org.opencv.core.Core; instead of org.opencv.videoio.VideoCapture.VideoCapture_3() like your error above...