This assignment covers the more advanced multithreading topics _futures_ and _future chaining_.
Futures are a feature of Java 8 and can be compared to the concept of _promises_ in JavaScript.
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@@ -12,13 +11,13 @@ For example [this one](http://www.deadcoderising.com/java8-writing-asynchronous-
_This is the CLI variant of the assignment. There's also an [Android variant](https://github.com/ohm-softa/11-futures-android) which covers the same concepts. **You don't have to implement both!** If you want to switch between them you should be able to copy most of the code you already wrote (except a few platform adoptions)._
## Setup
1. Create a fork of this repository (button in the right upper corner)
1. Clone the project (get the link by clicking the green _Clone or download button_)
1. Import the project to your **IntelliJ**
## Retrofit and `CompletableFuture`s
Inspect the interface `ohm.softa.a11.openmensa.OpenMensaAPI`.
The method return types have been changed from `Call<>` to `CompletableFuture<>`, a built-in way to leverage asynchronous programming via futures.
_Remark: the given unit tests won't succeed until you have completed the first part of this assignment as they require the `CompletableFuture<>` Call Adapter registered in Retrofit!_
## Retrieving all canteens
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### Retrieve the first page of canteens
Use the method `getCanteens()` of the OpenMensaAPI to retrieve the fist page of canteens (without index).
The method returns an instance of `Response<List<Canteen>>`.
The future returns an instance of `Response<List<Canteen>>`.
That might be a little bit confusing but the OpenMensaAPI does not expose a dedicated pagination endpoint to retrieve the total count of items or the total count of pages but exposes this information in the response headers (`X-Total-Pages`, `X-Total-Count`, ...).
To be able to extract this information you need the `Response<>` wrapper because the wrapper includes a reference to the headers.
### Extract the pagination information
There's a given utility class `PageInfo` which extracts the pagination information from a generic `Response<>` object. To create a `PageInfo` instance use the static factory method `PageInfo.extractFromResponse(...)`.
There's a given utility class `PageInfo` which extracts the pagination information from a generic `Response<>` object.
To create a `PageInfo` instance use the static factory method `PageInfo.extractFromResponse(...)`.
