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

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

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

List initList =testMain.newsList;//待賦值集合

List otherList = new ArrayList<>();//單個屬性排序，按title字符串排序

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

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

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

.collect(Collectors.toList());//多個屬性排序, 按title、hitNum倒序

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

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

.collect(Collectors.toList());//多個屬性排序，按title、hot排序降序，hot需轉成數字進行排序

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

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

.collect(Collectors.toList());//集合過濾，hot大于30的數據

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

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

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

ArrayList::new));//從 List 中取出title屬性的組成 新的list 集合

List titleList =initList.stream().map(News::getTitle).collect(Collectors.toList());//List轉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()));//單個屬性分組，title分組

Map> titleMap =initList.stream().collect(Collectors.groupingBy(News::getTitle));//多個屬性分組，title、author分組，groupingBy可以為多個

Map>> titleAndAuthorMap =initList.stream().collect(Collectors.groupingBy(News::getTitle, Collectors.groupingBy(News::getAuthor)));//利用stream().map()處理List，并給另外一個List賦值

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

initList.forEach(news ->{

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

});//map遍歷

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

System.out.println(k);

Map> map =v;

});

}//代碼塊初始化數據

{int i = 50;while (i > 0) {//1-5隨機數

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

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

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--;

}

}/*** 測試內部類*/@DataclassNews {//標題

privateString title;//作者

privateString author;//內容

privateString content;//點擊數

private inthits;//熱度

privateString hot;

}

}

總結

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