public class MemoryTesterActivity extends AppCompatActivity {

    List<String> memoryHog;

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

        memoryHog = new ArrayList<>();
        for(double i = 0; i < 1000000; i++){
            String number = Double.toString(i);
            memoryHog.add(number);
        }

    }

    public void asynctaskexecute(View target){
        new MyAsyncTask().execute();
    }

    private class MyAsyncTask extends AsyncTask {
        @Override
        protected Object doInBackground(Object[] params) {
            return doSomeStuff();
        }
        private Object doSomeStuff() {
            //do something to get result
            return new Object();
        }
    }
}