# Below is the interface for Iterator, which is already defined for you.
#
# class Iterator(object):
#     def __init__(self, nums):
#         """
#         Initializes an iterator object to the beginning of a list.
#         :type nums: List[int]
#         """
#
#     def hasNext(self):
#         """
#         Returns true if the iteration has more elements.
#         :rtype: bool
#         """
#
#     def next(self):
#         """
#         Returns the next element in the iteration.
#         :rtype: int
#         """

class PeekingIterator(object):
    def __init__(self, iterator):
        """
        Initialize your data structure here.
        :type iterator: Iterator
        """
        self.iterator = iterator
        self.cached = False

    def peek(self):
        """
        Returns the next element in the iteration without advancing the iterator.
        :rtype: int
        """
        if not self.cached:
            self.cache = self.iterator.next()
            self.cached = True
        return self.cache
        

    def next(self):
        """
        :rtype: int
        """
        if self.cached:
            self.cached = False
            return self.cache
        return self.iterator.next()
        

    def hasNext(self):
        """
        :rtype: bool
        """
        return self.iterator.hasNext() or self.cached

# Your PeekingIterator object will be instantiated and called as such:
# iter = PeekingIterator(Iterator(nums))
# while iter.hasNext():
#     val = iter.peek()   # Get the next element but not advance the iterator.
#     iter.next()         # Should return the same value as [val].


###Java
```java
// Java Iterator interface reference:
// https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html
class PeekingIterator implements Iterator<Integer> {

    Integer cache;
    Iterator<Integer> itr;
	public PeekingIterator(Iterator<Integer> iterator) {
	    // initialize any member here.
	    this.itr = iterator;
	    this.cache = itr.next();
	}

    // Returns the next element in the iteration without advancing the iterator.
	public Integer peek() {
        return cache;
	}

	// hasNext() and next() should behave the same as in the Iterator interface.
	// Override them if needed.
	@Override
	public Integer next() {
	    int res = cache;
	    cache = itr.hasNext() ? itr.next() : null;
	    return res;
	}

	@Override
	public boolean hasNext() {
	    return cache != null || itr.hasNext();
	}
}