rxjava:2.0.6, rxandroid:2.0.1

gistfile1.java

private List<String> getHeavyList() {
    List<String> list = new ArrayList<>();

    list.add("First string");
    list.add("Second string");
    list.add("Third string");

    return list;
}

Single<List<String>> singleListObservable = Single.fromCallable(new Callable<List<String>>() {
    @Override
    public List<String> call() {
        return getHeavyList();
    }
});

Disposable disposable = singleListObservable
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribeWith(new DisposableSingleObserver<List<String>>() {
            @Override
            public void onSuccess(List<String> strings) {
                Log.i("RxJava", strings.toString());
            }

            @Override
            public void onError(Throwable e) {

            }
        });

// on configuration changes stop callable
disposable.dispose();