MainActivity.java

package org.gdgkl.androidapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import com.example.yourcompany.Calculator;

public class MainActivity extends AppCompatActivity {

    // Used to load the 'native-lib' library on application startup.
    static {
        System.loadLibrary("calculator");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Calculator calculator = Calculator.create();
        TextView tv = (TextView) findViewById(R.id.sample_text);
        tv.setText(calculator.summation(3, 3) + "");
    }

}