Asynchronous user request processing and caching

Objective

Develop a Java application that processes user requests asynchronously using CompletableFuture and caches the results in a Map interface instance for quick retrieval in future requests.

Requirements

1. Request processing module:

   • Implement a method processRequest(String userId) that simulates processing a user request based on their userId.
   • The processing can be a simulated task, like fetching user data from a database (mock this with a delay).
   • The result of the processing should be a UserData object (a simple class with user details).

2. Asynchronous execution:

   • Use CompletableFuture to handle the processing of requests asynchronously.
   • The processRequest method should return a CompletableFuture<UserData>.

3. Caching with ConcurrentHashMap:

   • Declare a Map<String, UserData> cache = new ConcurrentHashMap<>(); to cache the results of processed requests. NOTE: ConcurrentHashMap is a thread-safe implementation of the Map interface. We will cover it in details in next topics.
   • Before processing a request, check if the userId is already in the cache. If yes, return the cached result immediately.
   • After processing a request, store the result in the cache.

Expected output

The application should be able to process multiple user requests concurrently, returning results asynchronously. Repeated requests for the same userId should be served from the cache, significantly reducing the response time.

Input data:

String[] userIds = {"user1", "user2", "user3", "user1"}; // Note: "user1" is repeated

Console output:

Processed: UserData[userId=user1, details=Details for user1]
Processed: UserData[userId=user2, details=Details for user2]
Processed: UserData[userId=user1, details=Details for user1]
Processed: UserData[userId=user3, details=Details for user3]