PriorityQueue example

Main.java

import java.util.ArrayList;
import java.util.PriorityQueue;
import java.util.Comparator;

class Customer {
  private int timeOnHold;
  public Customer(int timeOnHold) {
    this.timeOnHold = timeOnHold;
  }

  public int getTimeOnHold() {
    return timeOnHold;
  }

  @Override
  public String toString() {
    return Integer.toString(timeOnHold);
  }
}

class CustomerComparator implements Comparator<Customer> {
  @Override
  public int compare(Customer a, Customer b) {
    return b.getTimeOnHold() - a.getTimeOnHold();
  }
}

class Main {
  public static PriorityQueue<Customer> prioritise(ArrayList<Customer> customers) {
    PriorityQueue<Customer> q = new PriorityQueue<>(new CustomerComparator());
    q.addAll(customers);
    return q;
  }

  public static void main(String[] args) {
    ArrayList<Customer> customers = new ArrayList<>();
    customers.add(new Customer(5872));
    customers.add(new Customer(413));
    customers.add(new Customer(74353));
    customers.add(new Customer(435));
    
    PriorityQueue<Customer> q = prioritise(customers);
    while (q.size() > 0) {
      System.out.println(q.poll());
    }
  }
}