程序填空import _______(1)_________;//填写第1空:集合包的导入public class TestDog { public static void main(String[] args) {Dog ououDog = new Dog("欧欧", "雪娜瑞");Dog yayaDog = new Dog("亚亚", "拉布拉多");Dog meimeiDog = new Dog("美美", "雪娜瑞");Dog feifeiDog = new Dog("菲菲", "拉布拉多");//第2 、3空:定义一个ArrayList的集合对象dogs____(2)_________dogs = new ________(3)_________();dogs.add(ououDog);dogs.add(yayaDog);dogs.add(meimeiDog);// 第4空:添加feifeiDog到集合dogs中指定的第3个位置_______(4)_________;//第5空:填写方法:求集合dogs中元素的个数System.out.println("共计有" + _______(5)_________ + "条狗狗。");System.out.println("分别是:");for (int i = 0; i < dogs.size(); i++) {//第6空:填写方法:获取第i位置上的元素Dog dog = (Dog) dogs._______(6)_________;dog.showDog();}//使用迭代器遍历集合System.out.println("使用迭代器遍历集合:");Iterator it=dogs.iterator();while(_______(7)_________) {//第7空:判断集合中下一个元素是否存在Dog dog=(Dog)it.next();dog.showDog();}}}