jna

package help1;


import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Platform;


public class test1 {
        public interface CLibrary extends Library{
        CLibrary  INSTANCE = (CLibrary)
        Native.loadLibrary((Platform.isWindows() ? "msvcrt" : "c"),
                          CLibrary.class);
        void printf(String a,String s);
        }
public static void main(String[] args) {
// TODO Auto-generated method stub
                CLibrary.INSTANCE.printf("Hello,Word\n","abc");
                CLibrary.INSTANCE.printf("Hello,Word\n","der");
                
                
}

}

我的控制台打印的是两个换行的Hello, World,为什么我的abc和der没有被打印出来？