Question

In the following code snippet, I am not very clear about the usefulness of

Product other = (Product)obj;

It seems to me that it is redundant. Can we just remove this one, and change “return this.id==other.id” to “return this.id == obj.id”?

public class Product{
  String description;
  double price;
  int id;

  public Product(String d, double p, int i){
    description = d;
    price = p;
    id = i;
  }

  public boolean equals(Object obj){
    if(!(obj instanceof Product){
      return false;
    }
    Product other = (Product)obj;
    return this.id == other.id;
  }

  public int hashcode(){
    return id;
  }

  public String toString(){
    return id + " "+description;
  } 
}

Answer 1

The idea there is that you need to tell the language to treat other as a Product. Until you do, it only sees it as an Object, which doesn’t have an id attribute.