PriorityQueue question

[j2me64]

it looks like a lot of code but the code is very simple. i got a class Person

package priorityqueue2;

public class Person {
	private String name;
	
	public Person(String n) {
		this.name = n;
	}
	
	public String getName() {
		return this.name;
	}
	
	public String toString() {
		return this.name;
	}
}

and a class that implements the Comparator for the Person

package priorityqueue2;

import java.util.Comparator;

public class NameComparator implements Comparator {
	public int compare(Object o1, Object o2) {
		Person p1 = (Person)o1;
		Person p2 = (Person)o2;
		return p1.getName().compareTo(p2.getName());
	}
}

and i'm testing the PriorityQueue with the following code

package priorityqueue2;

import java.util.Iterator;
import java.util.PriorityQueue;

public class PriorityQueueExample {
	public static void main(String[] args) {
		PriorityQueue<Person> persons = new PriorityQueue<Person>(5, new NameComparator());
		Person p3 = new Person("Noah");
		persons.add(p3);
		Person p1 = new Person("Digobert");
		persons.add(p1);
		Person p2 = new Person("Dagobert");
		persons.add(p2);
		
		Iterator<Person> itr = persons.iterator();
		while (itr.hasNext()) {
			System.out.println(itr.next());
		}
	}
}

when i run the code the result is

Dagobert
Noah
Digobert


when i instantiate the priorityqueue i'm telling to use the NameComparator for sorting. so i expect that Digobert is before Noah. can somebody give an explanation about the order in the output?

[Tr1aL]

        PriorityQueue<Person> persons = new PriorityQueue<Person>(5, new NameComparator());
        Person p3 = new Person("Noah");
        persons.add(p3);
        Person p1 = new Person("Digobert");
        persons.add(p1);
        Person p2 = new Person("Dagobert");
        persons.add(p2);


        while (persons.size() != 0) {
            Person p = persons.remove();
            System.out.println(p);
        }

[JosAH]

The iterator for a priority queue iterates over all elements in the queue in a rando order (i.e. not the order in which the elements are logically ordered). See also the API documentation for the PriorityQueue class, it mentions a way to retrieve all elements in an ordered manner.

kind regards,

Jos

[j2me64]

The iterator for a priority queue iterates over all elements in the queue in a rando order (i.e. not the order in which the elements are logically ordered). See also the API documentation for the PriorityQueue class, it mentions a way to retrieve all elements in an ordered manner.

the api is your friend and says "The iterator does not return the elements in any particular order". so far, all clear about the iterator with priority queues. other question: is the method remove() the only way to get the elements in an ordered way?

Looking a little closer to the api i found "If you need ordered traversal, consider using Arrays.sort(pq.toArray())".

[JosAH]

the api is your friend and says "The iterator does not return the elements in any particular order". so far, all clear about the iterator with priority queues. other question: is the method remove() the only way to get the elements in an ordered way?

Looking a little closer to the api i found "If you need ordered traversal, consider using Arrays.sort(pq.toArray())".

Yep, and since you're using a comparator in your PriorityQueue object you can do this:

Arrays.sort(pq.toArray(), pq.comparator());

kind regards,

Jos