KITFORMA · EDITORIAL ANSWER
Why do BigDecimal values 2.0 and 2.00 behave differently in a HashSet?
KitForma editorial guide. Your domain may mean numeric equality while the object also retains a representation scale. Decide which distinction the collection must preserve.
Step-by-step answer
Your domain may mean numeric equality while the object also retains a representation scale. Decide which distinction the collection must preserve.
If two measurements are equal by numeric value, compare them with compareTo returning zero. For hashed keys, define a stable normalization rule before insertion, or use a value object whose equality and hash code implement the same rule. Do not replace equals alone while keeping an incompatible hash code. If reported precision matters, retaining both representations can be correct.
Test duplicate insertion, contains and removal for differently scaled values. Also test zero and negative scale after normalization. Changing equality semantics can merge previously distinct records; migrate persisted keys deliberately rather than treating this as a formatting-only change.
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