9. Host Platform Interoperability with Java and JavaScript

Activity 9.01: Book-Ordering Application

Solution:

1. Create a new project:

   lein new app books-app

2. Import the necessary namespaces:

   (ns books-app.core
     (:require [books-app.utils :as utils])
     (:import [java.util Scanner])
     (:gen-class))

3. Create a map to hold books by year:

   (def ^:const books {:2019 {:clojure {:title "Hands-On Reactive Programming with Clojure" :price 20}
                              :go      {:title "Go Cookbook" :price 18}}
                       :2018 {:clojure {:title "Clojure Microservices" :price 15}
               ...