LeetCode 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     Iterator<Integer> it;
 5     boolean isPeeked = false;
 6     Integer peekVal = null;
 7 
 8     public PeekingIterator(Iterator<Integer> iterator) {
 9         // initialize any member here.
10         this.it = iterator;
11     }
12 
13     // Returns the next element in the iteration without advancing the iterator.
14     public Integer peek() {
15         if(!isPeeked){
16             isPeeked = true;
17             peekVal = it.next();
18         }
19         return peekVal;
20     }
21 
22     // hasNext() and next() should behave the same as in the Iterator interface.
23     // Override them if needed.
24     @Override
25     public Integer next() {
26         if(!isPeeked){
27             return it.next();
28         }
29         isPeeked = false;
30         return peekVal;
31     }
32 
33     @Override
34     public boolean hasNext() {
35         return isPeeked || it.hasNext();
36     }
37 }