Question

I want to keep two things in my priority queue…one is a number and the other is cost. i.e. I want to do the following:

PriorityQueue<Integer, Cost> q=new PriorityQueue<Integer, Cost>();

Cost is another class that i hav:

class Cost implements Comparable<Cost>
{
  String name;
  double cost;

  @Override
  public int compareTo(Cost s)
  {
    return Double.compare(cost, s.cost);
  }
 }

Also I want to perform comparisons only based on cost…but I also want some integer identifier to be passed along with cost…is there some way to achieve this?

i need to retrieve Cost based on id..therefore I am using a hash map for it. When using an id field in cost…i want to retrieve the entire cost instance based on that id field…is it possible…is yes, then how?

I am a novice at Java programming. Can someone pls suggest some way out?

Answer 1

Change your Cost class

public class Cost implements Comparable<Cost> {
    String name;
    double cost;
    int id;

    public Cost(int id, String name, double cost) {
        this.id = id;
        this.name = name;
        this.cost = cost;
    }

    @Override
    public int compareTo(Cost s) {
        return Double.compare(cost, s.cost);
    }

    public int getId() {
        return this.id;
    }

    @Override
    public String toString() {
        return new StringBuilder().append("id : ").append(id).append(
                " name: ").append(name).append(" cost :").append(cost)
                .toString();

    }
}

Then you can simply declare PriorityQueue of Const

PriorityQueue<Cost> q=new PriorityQueue<Cost>();

Now when you want to find Cost based on id you can do below

PriorityQueue<Cost> queue = new PriorityQueue<Cost>();
    queue.add(new Cost(1, "one", 1));
    queue.add(new Cost(2, "two", 2));
    int id = 2;// Id to be found
    for (Cost cost : queue) {
        if (cost.getId() == 2) {
            System.out.println(cost);
        }
    }