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CompletableFuture

What is CompletableFuture?

Supports asynchronous programming in Java
A class that implements Future and CompletionStage
- What is Future?
  - A class that represents the result of an asynchronous operation
    - It allows you to know the result of a scheduled task
  - It can pass processed data to another thread in a multi-thread environment
  - Since it is implemented as Thread-Safe internally, there is no need to use synchronized blocks
It makes the following tasks, which were difficult with Future, much easier
- A Future cannot be completed externally
  - You cannot cancel it or set a timeout on get()
- Without using blocking code (get()), you cannot execute a callback when the task finishes
  - Any work that creates a result value through a Future and does something with it must come after get()
- Multiple Futures cannot be combined
  - ex) Fetching event information and then fetching the list of members who participated in the event
- It does not provide an API for exception handling