//RxJava2 Map操作符
        /**
         * Map操作符的作用就是將Observable所傳送送的資訊進行格式轉換或者處理，
         * 然後轉變為另外一個型別，傳送給Observer
         */
        Observable.create(new ObservableOnSubscribe<Integer>() {
            int i = 0;

            @Override
            public void subscribe(@NonNull ObservableEmitter<Integer> e) throws Exception {
                while (i < 3) {
                    Log.d("MainActivity", "Observable on " + Thread.currentThread().getName() + " emit " + i);
                    e.onNext(i);
                    i++;
                }
            }
        }).subscribeOn(Schedulers.io())
                //map操作符，Function<Object,Object>，只要型別為Object的子類就可以進行轉換
                .map(new Function<Integer, String>() {
                    //這個就是轉換的函式，返回的是轉換結果
                    @Override
                    public String apply(@NonNull Integer integer) throws Exception {
                        return "This is a String Type:" + integer;
                    }
                })
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Observer<String>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(String s) {
                        //這裡接收的就是一個String型別了
                        Log.d("MainActivity", "Observer on " + Thread.currentThread().getName() + " Receive:" + s);
                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                });