importlombok.Data;import java.util.*;importjava.util.stream.Collectors;public classTestMain {//测试集合

private List newsList = new ArrayList<>();public static voidmain(String[] args) {

TestMain testMain= newTestMain();//初始集合

List initList =testMain.newsList;//待赋值集合

List otherList = new ArrayList<>();//单个属性排序，按title字符串排序

List titleSortList =initList.stream().sorted(Comparator.comparing(News::getTitle)).collect(Collectors.toList());//多个属性排序, 按title、author字符串排序 thenComparing可以多个...

List titleAndAuthorSortList =initList.stream().sorted(Comparator.comparing(News::getTitle)

.thenComparing(Comparator.comparing(News::getAuthor)))

.collect(Collectors.toList());//多个属性排序, 按title、hitNum倒序

List titleAndHitsSortList =initList.stream().sorted(Comparator.comparing(News::getTitle)

.thenComparing(Comparator.comparing(News::getHits).reversed()))

.collect(Collectors.toList());//多个属性排序，按title、hot排序降序，hot需转成数字进行排序

List titleAndHotSortList =initList.stream().sorted(Comparator.comparing(News::getTitle)

.thenComparing((v1, v2)->Integer.valueOf(v2.getHot()).compareTo(Integer.valueOf(v1.getHot()))))

.collect(Collectors.toList());//集合过滤，hot大于30的数据

List hotFilterList = initList.stream().filter(news -> news.getHits() > 30).collect(Collectors.toList());//按照title/content字段进行去重

List titleRepeatList =initList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(

()-> new TreeSet<>(Comparator.comparing(o -> o.title +o.content))),

ArrayList::new));//从 List 中取出title属性的组成 新的list 集合

List titleList =initList.stream().map(News::getTitle).collect(Collectors.toList());//List转Map key:title,value:content；使用去重后的集合防止key不唯一

Map titleAndContentMap = titleRepeatList.stream().collect(Collectors.toMap(o -> o.getTitle(), o ->o.getContent()));//单个属性分组，title分组

Map> titleMap =initList.stream().collect(Collectors.groupingBy(News::getTitle));//多个属性分组，title、author分组，groupingBy可以为多个

Map>> titleAndAuthorMap =initList.stream().collect(Collectors.groupingBy(News::getTitle, Collectors.groupingBy(News::getAuthor)));//利用stream().map()处理List，并给另外一个List赋值

otherList = initList.stream().map(news -> {returnnews;}).collect(Collectors.toList());//list遍历

initList.forEach(news ->{

System.out.println(news.getContent());

});//map遍历

titleAndAuthorMap.forEach((k,v) ->{

System.out.println(k);

Map> map =v;

});

}//代码块初始化数据

{int i = 50;while (i > 0) {//1-5随机数

int num = (int) (Math.random() * 5 + 1);//1-50随机数

int hitNum = (int) (Math.random() * 50 + 1);//1-500随机数

int hotNum = (int) (Math.random() * 500 + 1);

News news= newNews();

news.setTitle("title" +num);

news.setAuthor("author" +num);

news.setContent("content" +num);

news.setHits(hitNum);

news.setHot(hotNum+ "");

newsList.add(news);

i--;

}

}/*** 测试内部类*/@DataclassNews {//标题

privateString title;//作者

privateString author;//内容

privateString content;//点击数

private inthits;//热度

privateString hot;

}

}