Friday, November 15, 2013

Example of LinkedList vs PriorityQueue

This example demonstrate the natural ordering of PriorityQueue.

natural ordering of PriorityQueue
Natural ordering of PriorityQueue
java.util.LinkedList is a doubly-linked list implementation of the List and Deque interfaces. Implements all optional list operations, and permits all elements (including null).

java.util.PriorityQueue is an unbounded priority queue based on a priority heap. The elements of the priority queue are ordered according to their natural ordering, or by a Comparator provided at queue construction time, depending on which constructor is used. A priority queue does not permit null elements. A priority queue relying on natural ordering also does not permit insertion of non-comparable objects (doing so may result in ClassCastException).

Example code:
package java_priorityqueue;

import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Random;

 * @web
public class Java_PriorityQueue {

    public static void main(String[] args) {

        int len = 5;
        Random random = new Random();

        PriorityQueue<Integer> priorityQueue = new PriorityQueue<>(len);
        LinkedList<Integer> linkedList = new LinkedList<>();

        System.out.println("Random number generated:");
        for (int i = 0; i < len; i++) {
            Integer randomNumber = new Integer(random.nextInt(100));
            linkedList.add(new Integer(randomNumber));
            priorityQueue.add(new Integer(randomNumber));
            System.out.println(i + ": " + randomNumber);
        System.out.println("Number in linkedList:");
        for (int i = 0; i < len; i++) {
            Integer item = linkedList.poll();
            System.out.println(i + ": " + item);
        System.out.println("Number in priorityQueue:");
        for (int i = 0; i < len; i++) {
            Integer item = priorityQueue.poll();
            System.out.println(i + ": " + item);

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