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javainheritancecomparison
Yunus
Yunus

Reputation: 23

Comparing objects of different classes derived from the same base

I have two classes, let's say DerivedOne and DerivedTwo, derived from a base class Base.

Assuming I have these:

DerivedOne d1;
DerivedTwo d2;

when I compare d1 and d2, I'd like d1 to always be smaller, in other words an object of DerivedOne should have a higher priority than an object of DerivedTwo. What is the best/nicest way to do that?

Upvotes: 2

Views: 603

Answers (4)

Averroes
Averroes

Reputation: 4228

Make both objects implements Comparable<Derivedparent> interface (or parent implements and subclass override) and then in the CompareTo method put something like this:

public class DerivedOne{

public int compareTo(DerivedParent dp){
 if (dp.instanceOf(DerivedTwo){
  return -1;
 }
 //More comparisons
}
}


public class DerivedTwo{

public int compareTo(DerivedParent dp){
 if (dp.instanceOf(DerivedOne){
  return 1;
 }
 //More comparisons
}
}

Upvotes: 2

nobeh
nobeh

Reputation: 10039

Most probably a proper implementation of java.util.Comparator<YourSuperClass>

Upvotes: 2

Sashi Kant
Sashi Kant

Reputation: 13465

In the super class declare a variable as priority.

And in the subclasses constructor, initialize that. 

class A
{
int priority;
}

class Derived1
{
 Derived1()
 {
  priority=1;
 }
}


class Derived2
{
Derived2()
{
priority=0;
}
}

Upvotes: 2

Matthew
Matthew

Reputation: 3946

I do not know if this is the nicest, but I would recommend using the instanceof operator inside the comparator.

Upvotes: 4

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