1 import java.util.Comparator;
2 import java.util.PriorityQueue;
3
4 /**
5 * 对集合使用Comparator，不改变对象的自然顺序
6 * @author Administrator
7 *
8 */
9 public class PriMsgQDemo {
10 public static void main(String[] args) {
11 Message m;
12 //自然顺序排列
13 PriorityQueue<Message> pq = new PriorityQueue<Message>(3);
14
15 pq.add(new Message("Message at main office at 3pm", Message.PLevel.Low));
16 pq.add(new Message("Fire in warehouse!", Message.PLevel.High));
17 pq.add(new Message("Report due Tuesday", Message.PLevel.Medium));
18
19 System.out.println("Message in natural-order priority: ");
20 while((m = pq.poll()) != null){
21 System.out.println(m.msg+"Priority: " + m.priority);
22 }
23 System.out.println();
24 //使用比较器
25 PriorityQueue<Message> pqRev = new PriorityQueue<Message>(3, new RevMsgComparer());
26
27 pqRev.add(new Message("Message at main office at 3pm", Message.PLevel.Low));
28 pqRev.add(new Message("Fire in warehouse!", Message.PLevel.High));
29 pqRev.add(new Message("Report due Tuesday", Message.PLevel.Medium));
30
31 System.out.println("Message in reverse-order priority: ");
32 while((m = pqRev.poll()) != null){
33 System.out.println(m.msg+"Priority: " + m.priority);
34 }
35 }
36 }
37
38 class Message implements Comparable<Message>{
39
40 String msg;
41 enum PLevel {
42 High, Medium, Low
43 }
44
45 PLevel priority;
46 public Message(String str, PLevel pri) {
47 msg = str;
48 priority = pri;
49 }
50
51 @Override
52 public int compareTo(Message o) {
53 return priority.compareTo(o.priority);
54 }
55
56 }
57
58 class RevMsgComparer implements Comparator<Message>{
59
60 @Override
61 public int compare(Message o1, Message o2) {
62 return o2.priority.compareTo(o1.priority);
63 }
64
65 }
