RxJava/RxAndroid : buffer(int count)

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import java.util.List;

import io.reactivex.Observable;
import io.reactivex.Observer;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.Disposable;
import io.reactivex.schedulers.Schedulers;

public class MainActivity extends AppCompatActivity {
    private String TAG = "输出";

    private Observer<List<Integer>> mObserver = new Observer<List<Integer>>() {
        @Override
        public void onSubscribe(Disposable d) {

        }

        @Override
        public void onNext(List<Integer> list) {
            Log.d(TAG, "onNext");
            for (int i = 0; i < list.size(); i++) {
                Log.d(TAG, "onNext:" + list.get(i));
            }
        }

        @Override
        public void onComplete() {
            Log.d(TAG, "onComplete");
        }

        @Override
        public void onError(Throwable e) {
            Log.e(TAG, e.toString(), e);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Integer[] numbers = new Integer[]{0, 1, 2, 3, 4};

        Observable.fromArray(numbers)
                .buffer(2)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeWith(mObserver);
    }
}

output:

01-19 17:02:45.736 18276-18276/? D/输出: onNext
01-19 17:02:45.736 18276-18276/? D/输出: onNext:0
01-19 17:02:45.736 18276-18276/? D/输出: onNext:1
01-19 17:02:45.736 18276-18276/? D/输出: onNext
01-19 17:02:45.736 18276-18276/? D/输出: onNext:2
01-19 17:02:45.736 18276-18276/? D/输出: onNext:3
01-19 17:02:45.736 18276-18276/? D/输出: onNext
01-19 17:02:45.736 18276-18276/? D/输出: onNext:4
01-19 17:02:45.736 18276-18276/? D/输出: onComplete