1 import java.util.*;
2 class Snow{}
3 class Powder extends Snow{}
4 class Crusty extends Snow{}
5 class Slush extends Snow{}
6
7 class Light extends Powder {}
8 class Heavy extends Powder {}
9
10
11 public class AddingGroups {
12
13 public static void main(String[] args) {
14
15 Collection<Integer> collection = new ArrayList<Integer>(Arrays.asList(1,2,3));
16 Integer[] moreInts = {4,5,6};
17 //Arrays.asList 顾名思义，传进去一个数组，搞出来一个List。数组转换为List
18 collection.addAll(Arrays.asList(moreInts));
19 Collections.addAll(collection, 7);//可变参数列表
20
21 /* Arrays.asList()的底层实现是用数组，因此不能调整尺寸。所以运行时会出现UnsupportedOperationException
22 List list = Arrays.asList(1,2,3);
23 list.add(4);
24 System.out.println(list);
25 */
26 System.out.println(collection);
27
28 List<Snow> snow1 = Arrays.asList(new Powder(),new Slush(),new Crusty());
29
30 List<Snow> snow2 = Arrays.asList(new Light(),new Heavy());
31
32 // Collections.addAll(snow2);
33
34 List<Snow> snow3 = new ArrayList<Snow>();
35
36 Collections.addAll(snow3, new Light(),new Heavy());
37
38 //显式类型参数说明
39 List<Snow> snow4 = Arrays.<Snow>asList(new Light(),new Heavy());
40
41
42 }
43
44 }
