Use of equals and inheritance

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Use of equals and inheritance

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#1 by (2 votes)

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I have a parent class and in it I have equals and I have other child classes of this parent class and I want to override equals to compare private attributes of those child classes but I also want to use equals of my father to compare the attributes inherited by my daughters, how would I do that without having to rewrite everything?

public class Pai {

   String nome;

   @Override
   public boolean equals(Object obj) {
      Pai other = (Pai) obj;
      return(this.nome.equals(other.nome);
   }

}

public class Filha extends Pai {
        int atributoEspecifico';

        @Override
        public boolean equals(Object obj) {
            // como comparo aquele atributo do meu pai também?
            Filha other = (Filha) obj;
            return this.atributoEspecifico == other.atributoEspecifico;
        }
    }

java equals

asked by anonymous 21.11.2014 / 04:36

1 answer

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score 2 · Answer 1

This is a typical use case for super :

Compare the instances using the superclass criteria;

If all is ok, compare also using the criteria of the class itself.

Code example (without handling errors, such as checking if the argument belongs to the right class):

public boolean equals(Object obj) {
    if ( !super.equals(obj) )
        return false;

    Filha other = (Filha) obj;
    return this.atributoEspecifico == other.atributoEspecifico;
}

Note that this works at any depth: if you create a Neta class that inherits from Filha , and call super.equals in it too, the Pai , Filha , and Neta , in that order.