get：
String url = "";
Request request = new Request.Builder() .url(url) .build();
Response response = client.newCall(request).execute();
return okHttpClient.newCall(request).execute().body().string();
post：
RequestBody requestBody = new FormBody.Builder().add("key1", value1).add("key2", value2).build();
String url = "";
OkHttpClient okHttpClient = new OkHttpClient();
Request request = new Request.Builder().url(url).post(requestBody).build();
return okHttpClient.newCall(request).execute().body().string();