Get方法是在子线程中获取网络数据，而且是同步的；

1.为什么Post方法不是从子线程向服务器推送呢？
2.Response难道也不用从子线程中相应吗？
3.Post和Response都是异步的，异步不用子线程吗？
上课代码如下：

private void post() {
        Request.Builder builder = new Request.Builder();
        builder.url(POST_URL);
        builder.post(RequestBody.create(MEDIA_TYPE_MARKDOWN, "Hello world github/linguist#1 **cool**, and #1!"));
        Request request = builder.build();
        Call call = mClient.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {

            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (response.isSuccessful()) {
                    final String content = response.body().string();
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            mContentTextView.setText(content);
                        }
                    });
                }
            }
        });
    }

    private void response() {
        Request.Builder builder = new Request.Builder();
        builder.url("https://raw.githubusercontent.com/square/okhttp/master/README.md");
        Request request = builder.build();
        Call call = mClient.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                Log.d(TAG, "onFailure() called with: call = [" + call + "], e = [" + e + "]");
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                Log.d(TAG, "onResponse() called with: call = [" + call + "], response = [" + response + "]");
                int code = response.code();
                Headers headers = response.headers();
                String content = response.body().string();
                final StringBuilder buf = new StringBuilder();
                buf.append("code: " + code);
                buf.append("\nHeaders: \n" + headers);
                buf.append("\nbody: \n" + content);
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        mContentTextView.setText(buf.toString());
                    }
                });
            }
        });
    }

    private void get() {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        executor.submit(new Runnable() {
            @Override
            public void run() {
                Request.Builder builder = new Request.Builder();
                builder.url("https://raw.githubusercontent.com/square/okhttp/master/README.md");
                Request request = builder.build();
                Log.d(TAG, "run: " + request);
                Call call = mClient.newCall(request);
                try {
                    Response response = call.execute();
                    if (response.isSuccessful()) {
                        final String string = response.body().string();
                        runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                mContentTextView.setText(string);
                            }
                        });
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        executor.shutdown();
    }