Backend.java

package com.example.android2111.app;

import java.util.List;

import retrofit2.Call;
import retrofit2.Retrofit;
import retrofit2.http.GET;
import retrofit2.http.Path;
import retrofit2.converter.gson.GsonConverterFactory

/**
 * Created by arneball on 2016-03-30.
 */
public class Backend {
    public interface FittUfc {
        @GET("/fighters") Call<List<User>> getFighters();
        @GET("/fighters/{id}") Call<User> getFighter(@Path("id") int id);
    }


    public static class User {
        public String name, surname;
    }

    public static final FittUfc UFC = new Retrofit.Builder()
            .baseUrl("http://ufc-data-api.ufc.com/api/v1/us")
            .addConverterFactory(GsonConverterFactory.create())
            .build()
            .create(FittUfc.class);
}

build.gradle

dependencies {
  compile 'com.squareup.retrofit2:retrofit:2.0.0'
  compile 'com.squareup.retrofit2:converter-gson:2.0.0'
}