Adam Heath wrote:
Adrian Crum wrote:
Adam Heath wrote:
ComparableRange has inconsistent access to the instance variables of
other ComparableRanges. There are several methods that do some kind
of comparison with another range. Sometimes, those methods call the
accessor methods. Other times, direct variable access is used.
Here's my take on this issue, based on the Concurrency in Practice
book. If ComparableRange is final, and not meant to be extended, then
always do direct access, period. If ComparableRange is supposed to be
extended by other classes, then make the instance variables final(to
force extended classes to use the accessors), then the base class
always must use the accessors.
Consistency would be nice. My personal preference is to avoid making
classes final because a user might want to extend a class's behavior.
That makes writing correct equals() and hashCode() very difficult.
a.equals(b) == b.equals(a) has to hold.
a.hashCode() == b.hashCode()
If the classes implement Comparable, then when a.equals(b),
a.compareTo(b) == 0 and b.compareTo(a) == 0.
When subclassing, and the subclass adds something that changes what
equals is based on, then all the other methods also have to be
changed, and all subclasses still have to obey the contracts outlined
above.
Those are very good points. Thank you for the reminder.
