OnJava8-Examples/collections/PriorityQueueDemo.java

// collections/PriorityQueueDemo.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.util.*;

public class PriorityQueueDemo {
  public static void main(String[] args) {
    PriorityQueue<Integer> priorityQueue =
      new PriorityQueue<>();
    Random rand = new Random(47);
    for(int i = 0; i < 10; i++)
      priorityQueue.offer(rand.nextInt(i + 10));
    QueueDemo.printQ(priorityQueue);

    List<Integer> ints = Arrays.asList(25, 22, 20,
      18, 14, 9, 3, 1, 1, 2, 3, 9, 14, 18, 21, 23, 25);
    priorityQueue = new PriorityQueue<>(ints);
    QueueDemo.printQ(priorityQueue);
    priorityQueue = new PriorityQueue<>(
        ints.size(), Collections.reverseOrder());
    priorityQueue.addAll(ints);
    QueueDemo.printQ(priorityQueue);

    String fact = "EDUCATION SHOULD ESCHEW OBFUSCATION";
    List<String> strings =
      Arrays.asList(fact.split(""));
    PriorityQueue<String> stringPQ =
      new PriorityQueue<>(strings);
    QueueDemo.printQ(stringPQ);
    stringPQ = new PriorityQueue<>(
      strings.size(), Collections.reverseOrder());
    stringPQ.addAll(strings);
    QueueDemo.printQ(stringPQ);

    Set<Character> charSet = new HashSet<>();
    for(char c : fact.toCharArray())
      charSet.add(c); // Autoboxing
    PriorityQueue<Character> characterPQ =
      new PriorityQueue<>(charSet);
    QueueDemo.printQ(characterPQ);
  }
}
/* Output:
0 1 1 1 1 1 3 5 8 14
1 1 2 3 3 9 9 14 14 18 18 20 21 22 23 25 25
25 25 23 22 21 20 18 18 14 14 9 9 3 3 2 1 1
      A A B C C C D D E E E F H H I I L N N O O O O S S
S T T U U U W
W U U U T T S S S O O O O N N L I I H H F E E E D D C C
C B A A
  A B C D E F H I L N O S T U W
*/