Why to use Retrofit?

Retrofit will save your development time, And also you can keep your code in developer friendly. Retrofit has given almost all the API's to make server call and to receive response. internally they also use GSON to do the parsing. you can go through this link you will get more info http://vickychijwani.me/retrofit-vs-volley/

Developing your own type-safe HTTP library to interface with a REST API can be a real pain: you have to handle many aspects, such as making connections, caching, retrying failed requests, threading, response parsing, error handling, and more. Retrofit, on the other hand, is a well-planned, documented and tested library that will save you a lot of precious time and headaches.

Volley v/s Retrofit see this link

http://vickychijwani.me/retrofit-vs-volley/

compile 'com.google.code.gson:gson:2.6.2'

compile 'com.squareup.retrofit2:retrofit:2.1.0'// compulsory

compile 'com.squareup.retrofit2:converter-gson:2.1.0' //for retrofit conversion