import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

/**

* Author : WindAsMe

* File : PeekingIterator.java

* Time : Create on 18-8-8

* Location : ../Home/JavaForLeeCode2/PeekingIterator.java

* Function : LeetCode No.284

*/

// Java Iterator interface reference:

// https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html

class PeekingIterator implements Iterator<Integer> {

private List<Integer> list;

public PeekingIterator(Iterator<Integer> iterator) {

// initialize any member here.

list = new ArrayList<>();

while (iterator.hasNext())

list.add(iterator.next());

}

// Returns the next element in the iteration without advancing the iterator.

public Integer peek() {

if (list.size() != 0)

return list.get(0);

return null;

}

// hasNext() and next() should behave the same as in the Iterator interface.

// Override them if needed.

@Override

public Integer next() {

if (list.size() != 0) {

Integer ans = list.get(0);

list.remove(0);

return ans;

}

return null;

}

@Override

public boolean hasNext() {

return list.size() != 0;

}

}