30.5 Conclusion

In retrospect, defining a correct implementation of equals has been surprisingly subtle. You must be careful about the type signature; you must override hashCode; you should avoid dependencies on mutable state; and you should implement and use a canEqual method if your class is non-final. Given how difficult it is to implement a correct equality method, you might prefer to define your classes of comparable objects as case classes. That way, the Scala compiler will add equals and hashCode methods with the right properties automatically.

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