ContactAPI Retrofit Interface

package com.example.kontakti;

import java.util.List;

import retrofit2.Call;
import retrofit2.http.Body;
import retrofit2.http.GET;
import retrofit2.http.DELETE;
import retrofit2.http.POST;
import retrofit2.http.PUT;
import retrofit2.http.Path;

public interface ContactAPI {
    public class message{
        public String status;
        public message(message m){
            this.status = m.status;
        }
        public message(String _status){
            this.status = _status;
        }
    }
    public class  contacts{
        public int ID;
        public String name;
        public String address;
        public String phone;
        public String email;
        public contacts(contacts m){
            ID = m.ID;
            name = m.name;
            address = m.address;
            phone = m.phone;
            email = m.email;
        }
        public contacts(int _ID, String _name, String _address,
                        String _phone, String _email){
            ID = _ID;
            name = _name;
            address = _address;
            phone = _phone;
            email = _email;
        }
    }
    @GET("/api/users")
    public Call<List<contacts>> api_users();

    @GET("/api/users/{id}")
    public Call<contacts> api_get_user(@Path("id") int id);

    @POST("/api/users/add")
    public Call<contacts> api_add_user(@Body contacts c);

    @PUT("/api/users/update")
    public Call<contacts> api_update_user(@Body contacts c);

    @DELETE("/api/users/delete/{id}")
    public Call<message> api_delete_user(@Path("id") int id);


}