Retrofit is a REST Client for Android and Java by Square
Retrofit is type-safe REST client for Android and Java which aims to make it easier to consume RESTful web services.
Here I have used api form http://tutorialheap.com to display Top 10 most populated countries in an android app. API: http://api.tutorialheap.com/worldpopulation/population
Used Retrofit to fetch data.
Check tutorial of this app here :
Download the App and check the result.