KITFORMA · EDITORIAL GUIDE
Why does a HashMap key become unfindable after one of its fields changes?
KitForma editorial guide. A key’s lookup identity must remain stable while it is stored. Changing fields used by equality or hashing can leave it in a location selected by its previous state.
Step-by-step guidance
A key’s lookup identity must remain stable while it is stored. Changing fields used by equality or hashing can leave it in a location selected by its previous state.
Prefer a small immutable key containing the actual identifier, separate from the editable record. If a key must change, remove the entry using its old stable state before modifying it, then insert the new key. Rebuilding the entire map may recover a test fixture, but it does not fix uncontrolled mutation in the application.
Reproduce with insertion, field mutation and containsKey. Then verify the replacement design keeps lookups and removals consistent. Immutability of the outer key is insufficient if its equality depends on a mutable nested collection.
Sources and verification
Sources checked:
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