Calculate gradient directions using java

Question

I'm trying to code a function that calculate an orientation or gradient directions of image without using the Built-in method in boofCV library which is

 GradientToEdgeFeatures.direction(derivX,derivY,orientation);

derivX is image derivative in x-direction. derivY is image derivative in Y-direction. orientation is image for storing the value of gradient directions. magnitude is image for storing the value of gradient directions. The output from the last Built-in method for 3x3 image=

Orientation 1.5707964
Orientation 1.5707964
Orientation 1.5707964
Orientation 1.5707964
Orientation 1.5707964
Orientation 1.5707964
Orientation 1.5707964
Orientation 1.5707964
Orientation 1.5707964

I wrote the code for this step and also for calculating the Magnitude as following:

         for (int i = 0; i < Orientation.getHeight(); i++) {
                for (int j = 0; j < orientation.getWidth(); j++) {
                    float valueOfOrientation =  (float) ((float)Math.atan2(derivY.get(j, i), derivX.get(j, i)));
                    orientation.set(j, i,valueOfOrientation);
                    System.out.println("Orientation"+valueOfOrientation );


                   }
                }

         for (int i = 0; i < (magnitude.getHeight()); i++) {
                for (int j = 0; j <( magnitude.getWidth()); j++) {

                    float valueXMag=(float) Math.pow(derivX.get(j, i),2);
                    float valueYMag=(float) Math.pow(derivY.get(j, i),2);
                    float magnitudeValue=(float) Math.sqrt(valueXMag+valueYMag);
                    magnitude.set(j, i,magnitudeValue );
                    System.out.println("Magnitude  "+magnitudeValue);

                    }
                }

But the value of output for 3x3 Image=

Orientation-1.5707964
Orientation-1.5707964
Orientation-1.5707964
Orientation-1.5707964
Orientation0.0
Orientation-1.5707964
Orientation-1.5707964
Orientation-1.5707964
Orientation-1.5707964

Magnitude 1.9073486E-6
Magnitude 1.9073486E-6
Magnitude 1.9073486E-6
Magnitude 1.9073486E-6
Magnitude 0.0
Magnitude 1.9073486E-6
Magnitude 1.9073486E-6
Magnitude 1.9073486E-6
Magnitude 1.9073486E-6

which is not equal to the Built-in method.
What is causing this and how can I solve this? Thanks in advance!

P.S Sorry for my writing mistakes. English in not my native language.