How to do intent to next XML if sharepreferences result is null?

I need help on going to next XML page if preferences result is null.

I have created two Java class which is activity_main and saving.

I do saving preferences in saving.java and retrieve the preferences is activity_main.

My activity_main doesn't have any preferences so it should prompt me to saving.java to save a preferences but when I tried to run the program, it didn't prompt me to saving.java and I find it weird.

Hope you guys could help me out with it, thanks

This is my activity_main code:

public class ActivityMain extends Activity {
    String tag = "Demo";
    Spinner greetingSpinner = null;

    protected ArrayAdapter<CharSequence> irAdapter;

    EditText nameEdit;
    int request_Code = 1;

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    public void onResume() {
        super.onResume();
        retrievePreferences();
        Log.d(tag, "In the onResume() event");
    }

    public void retrievePreferences() {

        SharedPreferences prefs = getSharedPreferences("preferences",
                MODE_PRIVATE);
        if (prefs.contains(null)) {
            Intent intent = new Intent("edu.nyp.activities.UserParticulars");
            startActivity(intent);
        } else {
            if (prefs.contains("greeting")) {
                String greetingString = prefs.getString("greeting", "");
                int iposition = irAdapter.getPosition(greetingString);
                greetingSpinner.setSelection(iposition);
            }
            if (prefs.contains("name")) {
                String nameString = prefs.getString("name", "");
                nameEdit.setText(nameString);
            }
        }
    }
}

This is my Saving.java code:

public class Saving extends Activity {
    String tag = "Demo";
    Spinner greetingSpinner = null;

    protected ArrayAdapter<CharSequence> irAdapter;

    EditText nameEdit;
    int request_Code = 1;

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

        Button saveBtn = (Button) findViewById(R.id.btn_Save);

        greetingSpinner = (Spinner) findViewById(R.id.spin_Greeting);
        this.irAdapter = ArrayAdapter.createFromResource(this,
                R.array.arrayGreeting, android.R.layout.simple_spinner_item);
        greetingSpinner.setAdapter(this.irAdapter);

        nameEdit = (EditText) findViewById(R.id.edit_Name);

        saveBtn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent intent = new Intent("android.intent.action.MAIN");

                Bundle extras = new Bundle();

                extras.putString("name", nameEdit.getText().toString());
                extras.putString("interestrate", greetingSpinner
                        .getSelectedItem().toString());

                intent.putExtras(extras);
                startActivityForResult(intent, request_Code);
            }
        });
    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == request_Code) {
            if (resultCode == RESULT_OK) {
                saveAsPreferences();
            }
        }
    }

    public void onPause() {
        super.onPause();
        saveAsPreferences();
        Log.d(tag, "In the onPause() event");
    }

    public void saveAsPreferences() {
        String nameString = nameEdit.getText().toString();
        String greetingString = greetingSpinner.getSelectedItem().toString();
        SharedPreferences prefs = getSharedPreferences("preferences",
                MODE_PRIVATE);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putString("greeting", greetingString);
        editor.putString("name", nameString);
        editor.commit();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
}