GLSL教程 第5章：光照和材质

题目：

题解：

class PeekingIterator<E> implements Iterator<E> {
    private Iterator<E> iterator;
    private E nextElement;

    public PeekingIterator(Iterator<E> iterator) {
        this.iterator = iterator;
        nextElement = iterator.next();
    }
    
    public E peek() {
        return nextElement;
    }
    
    @Override
    public E next() {
        E ret = nextElement;
        nextElement = iterator.hasNext() ? iterator.next() : null;
        return ret;
    }
    
    @Override
    public boolean hasNext() {
        return nextElement != null;
    }
}