Question

I have a project where I have a class Halfedge (olny .class file, so no way to modify it).
I want to create a PriorityQueue.
In order to determine which element is bigger, I need not only the fields inside the Halfedge class, but also a HashMap that I create in my code.

The thing is: when I define the Comparator class specific for the Halfedge, I cannot include any parameters.

My question is: how can I implement a comparator class for my Halfedge class using outside parameters? (or simply, how shoul I construct that PriorityQueue)

Thanks a lot!

Answer 1

Please take a look at the following code:

public class HalfedgeComparator
        implements Comparator<Halfedge>;
{

  Object param1 = null;

  public HalfedgeComparator (Object param1) {
    this.param1= param1;
  }

  public int compare(Halfedge item1, Halfedge item2)
  {
    return ...;
     //your logic here where you can use the param1 passed in the constructor
  }
}

and the client code may be:

Collections.sort(yourListHere, new HalfedgeComparator(yourExternalParamHere));