SCJP題庫第193題
Given that the elements of a PriorityQueue are ordered according to natural ordering, and:
2. import java.util.*;
3. public class GetInLine{
4. public static void main(String[] args){
5. PriorityQueue<String> pq = new PriorityQueue<String>();
6. pq.add("banana");
7. pq.add("pear");
8. pq.add("apple");
9. System.out.println(pq.poll() + " " + pq.peek());
10. }
11. }
What is the result?
A. apple pear
B. banana pear
C. apple apple
D. apple banana
E. banana banana
Ans: D
解說:
poll Retrieves and removes the head of this queue, or returns null if this queue is empty.
peek Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
PriorityQueue會讓加入的元素以字母順序排列
(HEAD) apple banana pear
poll取出apple印出，並將apple從queue移走，peed取出banana，不移出banana
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