// Instantiate the RequestQueue. 
    RequestQueue queue = Volley.newRequestQueue(getApplicationContext());
    String url = "http://www.google.com";

    // Request a string response from the provided URL. 
    StringRequest stringRequest = new StringRequest(url, new Response.Listener<String>() {
      @Override public void onResponse(String response) {
        //update ui

      }
    }, new Response.ErrorListener() {
      @Override public void onErrorResponse(VolleyError error) {
        //handle error

      }
    });
    // Add the request to the RequestQueue.
    queue.add(stringRequest);

     // Instantiate the RequestQueue. 
    RequestQueue queue = Volley.newRequestQueue(getApplicationContext());
    String url = "http://www.google.com";

     // Request a string response from the provided URL. 
    StringRequest stringRequest =
        new StringRequest(Request.Method.POST, url, new Response.Listener<String>() {
          @Override public void onResponse(String response) {

          }
        }, new Response.ErrorListener() {
          @Override public void onErrorResponse(VolleyError error) {

          }
        }) {
          @Override protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> params = new HashMap<String, String>();
            params.put("user", "deng");
            params.put("pass", "123"); 
            return params;
          }
        };

    // Add the request to the RequestQueue. 
    queue.add(stringRequest);

//为请求标记TAG
stringRequest.setTag(TAG); 
//将设置TAG的请求添加到请求队列中
mRequestQueue.add(stringRequest); 

//通过请求队列取消相同TAG的请求
mRequestQueue.cancelAll(TAG);

// Instantiate the RequestQueue. 
RequestQueue queue = Volley.newRequestQueue(getApplicationContext());
String url = "http://my-json-feed";

JsonObjectRequest jsObjRequest = new JsonObjectRequest
        (Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
    @Override
    public void onResponse(JSONObject response) {

    }
}, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {

    }
});

// Add the request to the RequestQueue. 
queue.add(request);

Cache cache = queue.getCache();
Entry entry = cache.get(url);
if(entry != null){
    try {
        String data = new String(entry.data, "UTF-8");
        // handle data, like converting it to xml, json, bitmap etc.,
    } catch (UnsupportedEncodingException e) {      
        e.printStackTrace();
        }
    }
}else{
    // Cached response doesn't exists. Make network call here
}

stringRequest.setShouldCache(false);

queue.getCache().remove(url);

queue.getCache().clear();

queue.getCache().invalidate(url,true);

OkHttpClient client = new OkHttpClient();

String run(String url) throws IOException {
  Request request = new Request.Builder()
      .url(url)
      .build();

  Response response = client.newCall(request).execute();
  return response.body().string();
}

public static final MediaType JSON
    = MediaType.parse("application/json; charset=utf-8");

OkHttpClient client = new OkHttpClient();

String post(String url, String json) throws IOException {
  RequestBody body = RequestBody.create(JSON, json);
  Request request = new Request.Builder()
      .url(url)
      .post(body)
      .build();
  Response response = client.newCall(request).execute();
  return response.body().string();
}

public final class BridgeInterceptor implements Interceptor {

  @Override public Response intercept(Chain chain) throws IOException {
    Request userRequest = chain.request();
    Request.Builder requestBuilder = userRequest.newBuilder();

    ...

    // 1.判断请求头信息"Accept-Encoding"是否存在
    // 2.如果是okhttp添加的"Accept-Encoding: gzip",那么也将负责解压缩
    // 3.如果原始请求头中存在"Accept-Encoding: gzip",那么okhttp不负责对响应进行解压缩,需要手动解压缩
    boolean transparentGzip = false;
    if (userRequest.header("Accept-Encoding") == null) {
      transparentGzip = true;
      requestBuilder.header("Accept-Encoding", "gzip");
    }

    ...

    // 4.发生网络传输,并获取响应
    Response networkResponse = chain.proceed(requestBuilder.build());

    Response.Builder responseBuilder = networkResponse.newBuilder().request(userRequest);

    // 5.判断响应头是否包含"Content-Encoding: gzip"字段,并且由okhttp负责解压缩
    if (transparentGzip
        && "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
        && HttpHeaders.hasBody(networkResponse)) {

      // 6.对响应进行解压缩
      GzipSource responseBody = new GzipSource(networkResponse.body().source());

      Headers strippedHeaders = networkResponse.headers()
          .newBuilder()
          .removeAll("Content-Encoding") // 7.移除"Content-Encoding"响应头字段
          .removeAll("Content-Length")   // 8.移除"Content-Length"响应头字段
          .build();
      responseBuilder.headers(strippedHeaders);
      responseBuilder.body(new RealResponseBody(strippedHeaders, Okio.buffer(responseBody)));
    }

    return responseBuilder.build();
  }
}

public interface GitHubService {
  @GET("users/{user}/repos")
  Call<List<Repo>> listRepos(@Path("user") String user);
}

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://api.github.com/")
    .build();

GitHubService service = retrofit.create(GitHubService.class);

Call<List<Repo>> repos = service.listRepos("octocat");

List<Repo> repositories = repos.execute().body();

repos.enqueue(new Callback<List<Repo>>() {
      @Override public void onResponse(Call<List<Repo>> call, Response<List<Repo>> response) {

      }

      @Override public void onFailure(Call<List<Repo>> call, Throwable t) {

      }
    });

@GET("/list")
Call<ResponseBody> list(@Query("page") int page);

.list(1) ===> /list?page=1

@GET("/list")
Call<ResponseBody> list(@Query("category") String category);

.list(null) ===> /list

@GET("/list")
Call<ResponseBody> list(@Query("category") String... categories);

.list("bar", "baz") ===> /list?category=bar&category=baz

 @GET("/search")
 Call<ResponseBody> list(@Query(value="foo", encoded=true) String foo);

.list() ===> .list("foo+bar")) yields /search?foo=foo+bar

public class DownloadWebPageTask extends AsyncTask<String, Voice, String> {

   ...

  @Override protected String doInBackground(String... urls) {

    String response = "";

    for (String url : urls) {

      try {
        InputStream inputStream = EffectiveHttpClient.retrieveService(url);
        BufferedReader buffered = new BufferedReader(new InputStreamReader(inputStream));

        String s = "";
        while ((s = buffered.readLine()) != null) {
          response += s;
        }
      } catch (IOException e) {
        //handle IOException

        //handle JSONException ?

        //handle inner Exception ?

        //handle Exception when nest call ?
      }
    }

    return response;
  }

  @Override protected void onPostExecute(String result) {
    mTextView.setText(result);
  }

  @Override protected void onCancelled(String result) {
    // handle cancel with result may be null
  }
}

private void retrieveMovies() {

    final Service service = ServiceGenerator.createService(Service.class);

    //1. 获取城市列表(网络操作)
    service.getCityList()
        .concatMap(new Func1<List<CityListResponse>, Observable<CityListResponse>>() {
          @Override
          public Observable<CityListResponse> call(List<CityListResponse> cityListResponses) {
            //2.依次取出"城市列表"集合中的元素
            return Observable.from(cityListResponses);
          }
        })
        .concatMap(new Func1<CityListResponse, Observable<List<MovieListResponse>>>() {
          @Override
          public Observable<List<MovieListResponse>> call(CityListResponse cityListResponse) {
            //3.根据每一个城市的id,获取该城市的电影列表(网络操作)
            return service.getMovies(cityListResponse.cityId);
          }
        })
        .concatMap(new Func1<List<MovieListResponse>, Observable<MovieListResponse>>() {
          @Override
          public Observable<MovieListResponse> call(List<MovieListResponse> movieListResponses) {
            //4.依次取出"电影列表"集合中的元素
            return Observable.from(movieListResponses);
          }
        })
        .concatMap(new Func1<MovieListResponse, Observable<MovieDetailResponse>>() {
          @Override
          public Observable<MovieDetailResponse> call(MovieListResponse movieListResponse) {
            //5.根据每一个电影的ID,获取该电影详情(网络操作)
            return service.getMovieDetail(movieListResponse.movieId);
          }
        })
        .subscribeOn(Schedulers.newThread())// 6.线程切换,上游的所有操作执行在工作线程
        .observeOn(AndroidSchedulers.mainThread())//7.线程切换,下游的所有将操作执行在UI线程
        .subscribe(new Subscriber<MovieDetailResponse>() {
          @Override public void onCompleted() {
          // finishCompletion
          }

          @Override public void onError(Throwable e) {
          //error handler
          }

          @Override public void onNext(MovieDetailResponse movieDetailResponse) {
            //8.根据电影ID所获取到的电影详情,该函数会被调用多次。
            textView.append(movieDetailResponse.movieName);
          }
        });
  }