Crash while running in simulator – Android Studio [duplicate]

public class MainActivity extends AppCompatActivity {

    Spinner pregPostWoman, chronicDiseases;
    EditText userAge;
    Button btnrecommend;
    TextView recommendExercise;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        userAge.findViewById(R.id.age);
        pregPostWoman.findViewById(R.id.pregnantWoman);
        chronicDiseases.findViewById(R.id.croDiseases);
        btnrecommend.findViewById(R.id.btnRecommend);
        recommendExercise.findViewById(R.id.textRecommend);

        ArrayAdapter<CharSequence> adapterPregPostWoman = ArrayAdapter.createFromResource(this, R.array.spinner_choise, android.R.layout.simple_spinner_item);
        adapterPregPostWoman.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        pregPostWoman.setAdapter(adapterPregPostWoman);

        ArrayAdapter<CharSequence> adapterChronicDiseases = ArrayAdapter.createFromResource(this, R.array.spinner_choise, android.R.layout.simple_spinner_item);
        adapterChronicDiseases.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        chronicDiseases.setAdapter(adapterChronicDiseases);

        btnrecommend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int age = Integer.parseInt(userAge.getText().toString());
                String spinnerPregPostWoman = pregPostWoman.getSelectedItem().toString();
                String spinnerChronicDiseases = chronicDiseases.getSelectedItem().toString();
                String recommendation = recommendExercise(age, spinnerPregPostWoman, spinnerChronicDiseases);
                recommendExercise.setText(recommendation);
            }
        });
    }

private String recommendExercise(int age, String spinnerPregPostWoman, String spinnerChronicDiseases){

        String recommendationExercise1 = "";
        String recommendationExercise2 = "";
        String combination = "";

        if (age >= 5 && age <= 17)
        {
            recommendationExercise1 = "Do exercise 60 minutes per day\n";
            recommendationExercise2 = "moderate to vigorous activity or vigorous activity (Running, Swimming, Biking, Jumping Rope)\n" +
                    "strengthening body (Jumping rope, Push-up, Dancing, Climbing, Aerobic)";
            combination = recommendationExercise1 + recommendationExercise2;
        }
        else if (age >= 18 && age <= 64)
        {
            if(spinnerPregPostWoman.equals("yes"))
            {
                combination = "150 minutes moderate activity (Brisk Walking, Tennis Double, Yoga, Gardening)\n" +
                        "aerobic and muscle - strengthening activities (umping rope, Push-up, Dancing, Climbing, Aerobic)";
            }
            else if(spinnerPregPostWoman.equals("no"))
            {
                if(spinnerChronicDiseases.equals("yes"))
                {
                    recommendationExercise1 = "Do functional balance activity (Standing 3 ways, Standing March, Side Step, Sit to Stand Balance)\n";
                    recommendationExercise2 = "Do 150–300 minutes of moderate-intensity aerobic physical activity (Brisk Walking, Tennis Double, Yoga, Gardening)\n" +
                            "or 75–150 minutes of vigorous-intensity aerobic physical activity (Running, Swimming, Biking, Jumping Rope)";
                    combination = recommendationExercise1 + recommendationExercise2;
                }
                else if(spinnerChronicDiseases.equals("no"))
                {
                    recommendationExercise1 = "Do 150–300 minutes of moderate-intensity aerobic physical activity (Brisk Walking, Tennis Double, Yoga, Gardening)\n" +
                            "or 75–150 minutes of vigorous-intensity aerobic physical activity (Running, Swimming, Biking, Jumping Rope)";
                    combination = recommendationExercise1;
                }
            }
        }
        else
        {
            recommendationExercise1 = "No matching exercises found. Please try different preferences.";
            combination = recommendationExercise1;
        }

        return combination;
    }
  

}

I try to make a recommendation of exercise using method if-else like in the code but the code have some problem. I don’t know how to identify it. The input comes from EditText and spinner. Then there is one button to generate the exercise.

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