how to solve the Error: Could not find or load main class in opencv3.0.0 with Java eclipse?

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I test the following HelloCV code of opencv3.0.0 with Java Eclipse neon and I got the error "could not find or load main class". How can I solve this?

package againtest;

import org.opencv.core.Core; import org.opencv.core.CvType; import org.opencv.core.Mat;

public class HelloCV { public static void main(String[] args){ System.loadLibrary(Core.NATIVE_LIBRARY_NAME); Mat mat = Mat.eye(3, 3, CvType.CV_8UC1); System.out.println("mat = " + mat.dump()); }

}