equals and hashCode

[Cyril Boulm�]

Hello,
In Cd-rom from book of Kathy Sierra and Bert Bates, the following question :

   
 
class SortOf{
 
  String name;
  int bal;
  String code;
  short rate;
 
  public int hashCode(){
    return (code.length*bal);
  }
 
  public boolean equals(Object o){
    //insert code here
  }
 
}
 

Which of the following will fulfill the equals() and the hashCode() contracts for this class?

Right Answer :

 
return (SortOf)o).code.length()*((SortOf)o).bal==this.code.length()*this.bal;
 
return ((SortOf)o).code.length()*((SortOf)o).bal*((SortOf)o).rate==this.code.length()*this.bal*this.rate;
 
   

But in the second correct answer, if o.code.length()=2, o.bal=3, o.rate=4 and this.code.length()=2, this.bal=4, this.rate = 3. The two objects are equals but there hashCode() are different, so the contract is bad.
Could you explain me?

Thanks

[Campbell Ritchie]

Please have a look at this thread about something similar. It might in fact be about the same question!

Any more problems, please fire away

[Cyril Boulm�]

You have right, I continue on the other thread