`DD.equals(DD)` does not override `Object.equals(Object)` — also violates clone and compareTo contracts

[shanjiang98]

Labels: bug

Body:

Summary

DD defines equals(DD y) (line 988) with parameter type DD instead of Object. This is
a method overload, not an override of Object.equals(Object). Standard Java APIs
(HashMap, HashSet, List.contains(), etc.) call equals(Object), which falls through
to Object.equals() (identity comparison).

Additionally, DD implements Comparable with a value-based compareTo() and Cloneable
with clone(), but since Object.equals() is not properly overridden, both the
compareTo-equals consistency and clone-equals contracts are violated.

How this was found

Detected by automated JDK conformance oracles (checkCompareToEqualsConsistency,
checkCloneEqualsConsistency).