In Java, the PriorityQueue class is implemented as a priority heap. Heap is an important data structure in computer science. For a quick overview of heap, here is a very good tutorial.
1. Simple Example
The following examples shows the basic operations of PriorityQueue such as offer(), peek(), poll(), and size().
import java.util.Comparator; import java.util.PriorityQueue; public class PriorityQueueTest { static class PQsort implements Comparator<Integer> { public int compare(Integer one, Integer two) { return two - one; } } public static void main(String[] args) { int[] ia = { 1, 10, 5, 3, 4, 7, 6, 9, 8 }; PriorityQueue<Integer> pq1 = new PriorityQueue<Integer>(); // use offer() method to add elements to the PriorityQueue pq1 for (int x : ia) { pq1.offer(x); } System.out.println("pq1: " + pq1); PQsort pqs = new PQsort(); PriorityQueue<Integer> pq2 = new PriorityQueue<Integer>(10, pqs); // In this particular case, we can simply use Collections.reverseOrder() // instead of self-defined comparator for (int x : ia) { pq2.offer(x); } System.out.println("pq2: " + pq2); // print size System.out.println("size: " + pq2.size()); // return highest priority element in the queue without removing it System.out.println("peek: " + pq2.peek()); // print size System.out.println("size: " + pq2.size()); // return highest priority element and removes it from the queue System.out.println("poll: " + pq2.poll()); // print size System.out.println("size: " + pq2.size()); System.out.print("pq2: " + pq2); } }Output:
pq1: [1, 3, 5, 8, 4, 7, 6, 10, 9] pq2: [10, 9, 7, 8, 3, 5, 6, 1, 4] size: 9 peek: 10 size: 9 poll: 10 size: 8 pq2: [9, 8, 7, 4, 3, 5, 6, 1]2. Example of Solving Problems Using PriorityQueue
Nearest points on a plane:
http://www.cnblogs.com/hygeia/p/5154490.html
Merge K sorted lists:
http://www.cnblogs.com/hygeia/p/5062768.html
3. Collections.sort也用到了这个comparator：
Insert Interval:
http://www.cnblogs.com/hygeia/p/5112649.html
转载于:https://www.cnblogs.com/hygeia/p/5159158.html
