Why is Android ActionBar drop down navigation using alot of RAM?

Why is Android ActionBar drop down navigation using alot of RAM?

My app is using alot of RAM (Cached background process) when I test on a
device.
I believe it is the ActionBar.
Why is the ActionBar drop down navigation using alot of RAM?
What is wrong with the following code?
And is it wrong to navigate between activities rather than fragments?
public class CreateWorkout extends ActionBarActivity implements
ActionBar.OnNavigationListener {
String[] dropDownValues = {"GYM WORKOUT", "MENU", "CREATE WORKOUT", "LOAD
WORKOUT", "TIMER"};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.create_workout);
final ActionBar actionBar = getSupportActionBar();
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
ArrayAdapter<String> adapter = new
ArrayAdapter<String>(actionBar.getThemedContext(),
android.R.layout.simple_spinner_dropdown_item, dropDownValues);
actionBar.setListNavigationCallbacks(adapter, this);
}
@Override
public boolean onNavigationItemSelected(int position, long arg1) {
switch(position){
case 0:
break;
case 1:
startActivity(new Intent(CreateWorkout.this, MainActivity.class));
break;
case 2:
startActivity(new Intent(CreateWorkout.this, CreateWorkout.class));
break;
case 3:
startActivity(new Intent(CreateWorkout.this, LoadWorkout.class));
break;
case 4:
startActivity(new Intent(CreateWorkout.this, WorkoutTimer.class));
break;
}
return false;
}
}