OkHttp download file by Okio

FileUtil.java

import android.os.Environment;
import android.support.annotation.NonNull;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.TimeUnit;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.ResponseBody;
import okhttp3.internal.Util;
import okio.Buffer;
import okio.BufferedSink;
import okio.BufferedSource;
import okio.Okio;
import rx.Observable;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;

public class FileUtil {

    public static Observable<Integer> downloadFileByOkio(@NonNull final String url, @NonNull final File destFile) {
        return Observable.create(new Observable.OnSubscribe<Integer>() {
            @Override
            public void call(Subscriber<? super Integer> subscriber) {

                BufferedSink sink = null;
                BufferedSource source = null;
                try {
                    Request request = new Request.Builder().url(url).build();
                    Response response = HttpClientUtil.getInstance().getOkHttpClient().newCall(request).execute();
                    ResponseBody body = response.body();
                    long contentLength = body.contentLength();
                    source = body.source();
                    sink = Okio.buffer(Okio.sink(destFile));
                    Buffer sinkBuffer = sink.buffer();
                    long totalBytesRead = 0;
                    int bufferSize = 8 * 1024;
                    long bytesRead;
                    while ((bytesRead = source.read(sinkBuffer, bufferSize)) != -1) {
                        sink.emit();
                        totalBytesRead += bytesRead;
                        int progress = (int) ((totalBytesRead * 100) / contentLength);
                        subscriber.onNext(progress);
                    }
                    sink.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                    subscriber.onError(e);
                } finally {
                    Util.closeQuietly(sink);
                    Util.closeQuietly(source);
                }

                subscriber.onCompleted();
            }
        }).throttleFirst(1, TimeUnit.SECONDS)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread());
    }

    public static Observable<Integer> downloadFile(final String url) {
        return Observable.create(new Observable.OnSubscribe<Integer>() {
            @Override
            public void call(Subscriber<? super Integer> subscriber) {
                InputStream inputStream = null;
                FileOutputStream outputStream = null;
                try {

                    System.out.println("start download " + Thread.currentThread().getName() + " time " + System.currentTimeMillis());

                    OkHttpClient client = HttpClientUtil.getInstance().getOkHttpClient();
                    Request request = new Request.Builder().url(url).build();
                    Response response = client.newCall(request).execute();
                    inputStream = response.body().byteStream();
                    outputStream = new FileOutputStream(new File(Environment.getExternalStorageDirectory(), "a.txt"));
                    int totalCount = inputStream.available();
                    byte[] buffer = new byte[2 * 1024];
                    int len;
                    int readLen = 0;
                    while ((len = inputStream.read(buffer)) != -1 ) {

                        //System.out.println("download loop " + Thread.currentThread().getName());

                        outputStream.write(buffer, 0, len);
                        readLen += len;
                        subscriber.onNext(readLen);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                    subscriber.onError(e);
                } finally {
                    try {
                        if (inputStream != null) {
                            inputStream.close();
                        }
                        if (outputStream != null) {
                            outputStream.close();
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }

                subscriber.onCompleted();
            }
        });
    }

}