284. Peeking Iterator

 80.54 %

class PeekingIterator implements Iterator<Integer> {

    Integer top = null;

    Iterator<Integer> iterator;

public PeekingIterator(Iterator<Integer> iterator) {

    // initialize any member here.

        this.iterator = iterator;

        if (this.iterator.hasNext()) top = this.iterator.next();

}

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

public Integer peek() {

        return top;

}

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

// Override them if needed.

@Override

public Integer next() {

    Integer result = top;

        if (iterator.hasNext()) {

            top = iterator.next();

        } else {

            top = null;

        }

        return result;

}

@Override

public boolean hasNext() {

    return top != null;

}

}