opencv android sdk ini source code available,and where can I get it?

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I hava get opencv android sdk java code ,but can't find any jni code such as those(from Mat.java):

// C++: Mat::Mat()
private static native long n_Mat();

// C++: Mat::Mat(int rows, int cols, int type)
private static native long n_Mat(int rows, int cols, int type);

// C++: Mat::Mat(Size size, int type)
private static native long n_Mat(double size_width, double size_height, int type);

So I wanna to know is those native code available ,where to get?

Thanks !