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equals and hashcode question

 
Ranch Hand
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Hello everyone.

Trying a mock exam from coderanch, I fall into the question below:

"Given the following class House, which code fragments can be added to complete the equals() method without breaking the contract for hashCode()?"


I've selected two correct answers, but there is an answer provided by the mock that I think it is wrong. That is:



I don't think the statement above are true, because running the code below, I get the output

hashCode: true
equals: false



tks
 
Rancher
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The documentation states

equal objects must have equal hash codes


It does not say that unequal objects must have unequal hash codes.
 
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Hash Code determines which bucket an Object goes into. There can be different Objects in the same bucket.


Object 1 and Object 2 can evaluate to the same Hash Code and end up in the same bucket. However, Object 1 is not equal to Object 2.
 
Adolfo Eloy
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Thanks for all reply.

But that's the point. When I was working on this question, I firstly was convinced about the concept that having two instances of the same class may have the same hashcode and be meaningfully unequal.
So, at this mock from coderanch, there was another answer that leads to the same situation (same hascode values and not equals) that follows:



Regarding this, the answers that follows must be considered valid to not break the hashCode's contract am I right?




tks
 
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This one will violate the contract. Consider the following:


Equals gives true, hashCodes are not equal.
 
Adolfo Eloy
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Thanks to all. I understand now.
 
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