list轉map Java Stream的使用

一、list ->map

1、有如下表對應表結構，實現

2、先進行一些簡單的操作

定義類

private integer rank;  

private string description;  
public movie(integer rank, string description)   
public integer getrank()   
public string getdescription() 
@override
public string tostring() 

直接遍歷將對應值put放入map

//建立乙個 listmovies

listmovies = new arraylist();  
movies.add(new movie(1, "the shawshank redemption"));  
movies.add(new movie(2, "the godfather"));  
for (movie movie : movies)   
//列印map
int rank=entry.getkey();
movie movie=entry.getvalue();
system.out.println(rank+":"+movie);
}

//建立乙個list

listmovies = new arraylist();  
movies.add(new movie(1, "the shawshank redemption"));  
movies.add(new movie(2, "the godfather"));

listranklist=movies.stream().map(p->p.getrank()).collect(collectors.tolist());

3、回到問題

listredbaggoodslist --->  listsusnapids 即：redbaggoods的ids(redbaggoodslist)獲取susnapinfo表的ids

listsusnapids = redbaggoodslist.stream().map(p->p.getsusnapid()).collect(collectors.tolist());

listgiftstatuslist = redbaggoodslist.stream().map(p -> p.getgiftstatus()).distinct().collect(collectors.tolist());

map> redbagid2redbagmap = redbaglist.stream().collect(collectors.groupingby(p->p.getredbagid()));

long sucount = susnapinfolist.stream().map(p->p.getsuname()).distinct().count();

listgiftids = redbaggoodslist.stream().map(p -> p.getgiftbagid()).filter(p -> p.equals(firstgiftids))

.collect(collectors.tolist());

比較簡單，只給出**

// 集合去重

listls1 = new arraylist<>();
ls1.add("a");
ls1.add("b");
ls1.add("c");
listls2 = new arraylist<>();
ls2.add("a");
ls2.add("b");
ls2.add("c");
ls2.add("d");
// 是否存在ls1完全包含ls2的情況
boolean exist = ls1.containsall(ls2);
if (!exist) 
system.out.println(ls2);// d

List排序轉map map再轉list

根據工單id查詢字段值 listformitemvaluevolist this.produceformdao.listformitemvaluebyworkorderid workorderid if formitemvaluevolist.isempty map formitemvaluevom...

form表單，轉Map，轉List

1 form表單包含，select下拉列表，input輸入框等，轉為map，js如下 var baseinfo var formarray baseinfo serializearray each formarray,function i,item 注 baseinfo baseinfo是form的...

json轉實體，json轉list

json轉換 注 以下全用的是com.alibaba.fastjson 1.實體轉string轉json user user new user user.age 18 user,name 張三 實體轉string string json json.tojsonstring result string...