PriorityQueueDemoJava

PriorityQueueDemo.java

import java.util.AbstractMap;
import java.util.Comparator;
import java.util.Map;
import java.util.PriorityQueue;

public class PriorityQueueDemo {
    public static void main(String[] args) {
        priorityQueueDemo1();
        priorityQueueDemo2();
        priorityQueueDemo3();
    }

    static void priorityQueueDemo1() {
        PriorityQueue<Integer> pq1 = new PriorityQueue<>();
        PriorityQueue<Integer> pq2 = new PriorityQueue<>(Comparator.reverseOrder());
        int[] arr = new int[] {10, 4, 2, 7, 1, 9, 3};
        for (int x : arr) {
            pq1.offer(x);
            pq2.offer(x);
        }
        while (!pq1.isEmpty()) {
            System.out.println(pq1.poll() + " " + pq2.poll());
        }
        System.out.println();
    }

    static void priorityQueueDemo2() {
        PriorityQueue<Map.Entry<Integer, Integer>> pq = new PriorityQueue<>((p1, p2) -> {
            if (p1.getKey() == p2.getKey())
                return p1.getValue() - p2.getValue();
            return p1.getKey() - p2.getKey();
        });
        int[] arr1 = new int[] {4, 3, 2, 7, 0, 4};
        int[] arr2 = new int[] {3, 6, 1, 9, 3, 10};
        for (int i = 0; i < arr1.length; i++)
            pq.offer(Pair.of(arr1[i], arr2[i]));

        while (!pq.isEmpty()) {
            Map.Entry<Integer, Integer> p = pq.poll();
            System.out.println(p.getKey() + " " + p.getValue());
        }
        System.out.println();
    }

    static void priorityQueueDemo3() {
        PriorityQueue<Map.Entry<String, Integer>> pq = new PriorityQueue<>(
                (p1, p2) -> {
                    if (p1.getValue() == p2.getValue())
                        return p1.getKey().compareTo(p2.getKey());
                    return p2.getValue().compareTo(p1.getValue());
                });

        String[] strArr = new String[] {"bob", "leonardo", "alex", "david", "monika"};
        int[] intArr = new int[] {2, 1, 2, 4, 2};
        for (int i = 0; i < strArr.length; i++) {
            Map.Entry<String, Integer> p = Main.Pair.of(strArr[i], intArr[i]);
            pq.offer(p);
        }

        while (!pq.isEmpty()) {
            Map.Entry<String, Integer> p = pq.poll();
            System.out.println(p.getKey() + " " + p.getValue());
        }
        System.out.println();
    }

    static class Pair {
        public static <T, U> Map.Entry<T, U> of(T first, U second) {
            return new AbstractMap.SimpleEntry<>(first, second);
        }
    }
}