KITFORMA · EDITORIAL ANSWER
Why does thenApply return a nested CompletableFuture instead of the final asynchronous result?
KitForma editorial guide. The callback itself returns another asynchronous stage, so ordinary mapping preserves that stage as a value. The caller then observes two completion levels.
Step-by-step answer
The callback itself returns another asynchronous stage, so ordinary mapping preserves that stage as a value. The caller then observes two completion levels.
Use thenCompose when the next function already returns a CompletionStage, for example
loadAccount().thenCompose(account -> loadSettings(account.id())). Use thenApply when producing an ordinary value. Do not fix the nesting by calling join inside a callback running on a constrained executor; blocking can reduce capacity or create dependency deadlocks.
Test failure and success from both the first and second stage. Confirm the returned future completes only when settings are actually available. Composition does not automatically cancel every underlying task, and execution-thread choice still depends on the selected async overloads and executors.Sources and verification
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