Question

I have a class

class Pair<T>{
    private T data;
    private T alternative;
}

Two pair objects would be equal if

this.data.equals(that.data) && this.alternative.equals(that.alternative) || 
this.data.equals(that.alternative) && this.alternative.equals(that.data)

I’m having difficulty correctly implementing the hashCode() part though. Any suggestions would be appreciated

Answer 1

This should do the trick:

  @Override
  public int hashCode() {
    return data.hashCode() * alternative.hashCode();
  }

Since you want to include both fields into the equals, you need to include both fields into the hashCode method. It is correct if unequal objects end up having the same hash code, but equal objects according to your scheme will always end up having the same hash code with this method.