持有对象

package holding;import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.List;class Snow{}class Power extends Snow{}class Light extends Power{}class Heavy extends Power{}class Crusty extends Snow{}class Slush extends Snow{}/** * 主要是Arrays.asList的用法值得注意，以及：在用它时，继承只管上一级 * @author fireliuwei * */public class AsListInterface {public static void main(String[] args) {   Snow snow = new Heavy();       List<Snow> snow1 = Arrays.asList(new Crusty(),new Slush(),new Power());      //下面这句话不能编译，原因自己看下就明白      //List<Snow> snow2 = Arrays.asList(new Light(),new Heavy());      List<Snow> snow3 = new ArrayList<Snow>();      Collections.addAll(snow3, new Light(),new Heavy());      List<Snow> snow4 = Arrays.<Snow>asList(new Light(), new Heavy());}}

package holding;import java.util.ArrayList;import java.util.Arrays;import java.util.Collection;import java.util.Collections;import java.util.List;public class AddingGroups {public static void main(String[] args) {Collection<Integer> collection = new ArrayList<Integer>(Arrays.asList(1, 2, 3, 4, 5));Integer[] moreInts = { 6, 7, 8, 9, 10 };collection.addAll(Arrays.asList(moreInts));Collections.addAll(collection, 11, 12, 13, 14, 15);Collections.addAll(collection, moreInts);@SuppressWarnings("unused")List<Integer> list = Arrays.asList(16, 17, 18, 19, 20);list.set(1, 99);//list.add(21);运行出错，因为Arrays.asList（）底层是固定大小数组，不可扩充的}}