Peeking Iterator

 1 // Java Iterator interface reference:
 2 // https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html
 3 class PeekingIterator implements Iterator<Integer> {
 4     private Integer peekElement;
 5     private boolean hasPeeked;
 6     private Iterator<Integer> iterator;
 7 
 8     public PeekingIterator(Iterator<Integer> iterator) {
 9         // initialize any member here.
10         this.iterator = iterator;
11         hasPeeked = false;
12     }
13 
14     // Returns the next element in the iteration without advancing the iterator.
15     public Integer peek() {
16         if (!hasPeeked) {
17             hasPeeked = true;
18             peekElement = iterator.next();
19         }
20         return peekElement;
21     }
22 
23     // hasNext() and next() should behave the same as in the Iterator interface.
24     // Override them if needed.
25     @Override
26     public Integer next() {
27         if (!hasPeeked) {
28             return iterator.next();
29         }
30         hasPeeked = false;
31         return peekElement;
32     }
33 
34     @Override
35     public boolean hasNext() {
36         return hasPeeked || iterator.hasNext();
37     }
38 }
posted on 2016-07-06 15:26 keepshuatishuati 阅读(120) 评论(0) 编辑收藏举报