java8 集合 多欄位 分組 統計個數程式碼
阿新 • • 發佈：2020-08-26
1.user實體
package com.demo.dto;
public class User {
private Integer id;
private String userName;
private String password;
private Integer age;
private long c;
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(Integer id,String userName,String password,Integer age) {
super();
this.id = id;
this.userName = userName;
this.password = password;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName == null ? null : userName.trim();
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password == null ? null : password.trim();
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public long getC() {
return c;
}
public void setC(long l) {
this.c = l;
}
@Override
public String toString() {
return "User [id=" + id + ",userName=" + userName + ",password=" + password + ",age=" + age + ",c=" + c
+ "]";
}
public static void main(String[] args) {
User u1=new User(1,"aa","aap",23);
User u2=new User(2,23);
User u3=new User(3,"bb",23);
User u4=new User(4,"cc",23);
User u5=new User(5,23);
User u6=new User(6,23);
User u7=new User(7,24);
List<User> list=new ArrayList<User>();
list.add(u1);list.add(u2);list.add(u7);list.add(u3);list.add(u4);list.add(u5);list.add(u6);
//原有list(根據第二個欄位:userName和第四個欄位:age 統計重複的記錄數)
//jdk8的方法統計個數:
Map<String,Map<Integer,Long>> map = list.stream().collect(Collectors.groupingBy(User::getUserName,Collectors.groupingBy(User::getAge,Collectors.counting())));
//jdk8以下:
Map<String,Long>> map=new HashMap<String,Long>>();
for (User user1 : list) {
Map<Integer,Long> value=new HashMap<Integer,Long>();
long count=0;
if(map.containsKey(user1.getUserName())){
continue;
}
for(int i=0;i<list.size();i++){
if(user1.getUserName().equals(list.get(i).getUserName())&&user1.getAge()==list.get(i).getAge()){
count+=1;
value.put(user1.getAge(),count);
map.put(user1.getUserName(),value);
}else if(user1.getUserName().equals(list.get(i).getUserName())&&user1.getAge()!=list.get(i).getAge()){
value.put(list.get(i).getAge(),Long.valueOf(1));
map.put(user1.getUserName(),value);
}
}
}
map.forEach((k,v) -> {
System.out.println(k+">>>>"+v);
});
List<User> list2=new ArrayList<User>();
list.forEach(user ->{
map.forEach((k,v) -> {
if(k==user.getUserName()){
Long remove = v.remove(user.getAge());
user.setC(null==remove?0:remove);
}
});
list2.add(user);
});
//遍歷最後想要的結果(User中c為統計後的個數，方便前臺遍歷集合時單元格合併行)
list2.forEach(u ->{
System.out.println(u);
});
}
}
備註：執行結果如下
cc>>>>{23=3}
bb>>>>{23=1}
aa>>>>{23=2,24=1}
User [id=1,userName=aa,password=aap,age=23,c=2]
User [id=2,c=0]
User [id=7,age=24,c=1]
User [id=3,userName=bb,c=1]
User [id=4,userName=cc,c=3]
User [id=5,c=0]
User [id=6,c=0]
此處是為了實現如下效果：
補充知識：List集合中元素按照固定數量進行分組
最近做專案，被要求將全國所有省份在頁面中展示出來，但是要求
1、字少的三個省份佔一行
2、字多的兩個省份佔一行
想來想去只能想到查詢出所有省份，然後分組返回資料，上程式碼
public Map<String,Object> campus_list_provence(HttpServletRequest request,HttpServletResponse response)throws Exception{
Map<String,Object> map=new HashMap<String,Object>();
String sql="查詢所有省份的名稱，可以先在資料庫中將全國所有省份建一個表";
List<String> list=bd.getSQLList(sql);
//建立第一個list1，裡面存入省份名稱少於4個字的
List<String> list1=new ArrayList<String>();
//建立第二個list2，裡面存入省份名稱大於4個字的
List<String> list2=new ArrayList<String>();
if(list!=null&&list.size()>0){
for (String string : list) {
if(string.length()>4){
list2.add(string);
}else{
list1.add(string);
}
}
}
int keyToken = 0;
int toIndex=3;
List<Object> listSortMap = new ArrayList<Object>();
for(int i = 0;i<list1.size();i+=3){
if(i+3>list1.size()){ //作用為toIndex最後沒有3條資料則剩餘幾條newList中就裝幾條
toIndex=list1.size()-i;
}
List newList = list1.subList(i,i+toIndex);
keyToken++;
listSortMap.add(newList);
}
int keyToken2 = 0;
List<Object> listSortMap2 = new ArrayList<Object>();
for(int i = 0;i<list2.size();i+=2){
if(i+2>list2.size()){ //作用為toIndex最後沒有2條資料則剩餘幾條newList中就裝幾條
toIndex=list2.size()-i;
}
List newList2 = list2.subList(i,i+toIndex);
keyToken2++;
listSortMap2.add(newList2);
}
map.put("prov1",listSortMap);
map.put("prov2",listSortMap2);
return map;
}頁面接收
function campus_list_ByProvence(req_data){
$.ajax({
type : "POST",url : "剛才方法的url",traditional: true,data : req_data,timeout : 20000,cache : false,beforeSend : function(XMLHttpRequest) {},success : function(data) {
/* 生成html */
$('#campus_list_provence').html(campus_list_ByProvenceHtml1(data.prov1,data.prov2));
},error : function() { alert("ajax失敗！");}
});
}
function campus_list_ByProvenceHtml1(prov,prov2){
var html = "";
for(var i = 0,j = prov.length ; i < j ; i++){
html+='<li class="li1" >';
if(prov[i][0]!=undefined&&prov[i][0]!=null&&prov[i][0]!=""){
var provstr0="'"+prov[i][0]+"'";
html+='<a href="#2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="GoToUrlItem('+provstr0+');">'+prov[i][0]+'</a>';
}else{
html+='';
}
if(prov[i][1]!=undefined&&prov[i][1]!=null&&prov[i][1]!=""){
var provstr1="'"+prov[i][1]+"'";
html+='<a href="#2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="GoToUrlItem('+provstr1+');">'+prov[i][1]+'</a>';
}else{
html+='';
}
if(prov[i][2]!=undefined&&prov[i][2]!=null&&prov[i][2]!=""){
var provstr2="'"+prov[i][2]+"'";
html+='<a href="#2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="GoToUrlItem('+provstr2+');">'+prov[i][2]+'</a>';
}else{
html+='';
}
html+='</li>';
}
for(var i = 0,j = prov2.length ; i < j ; i++){
html+='<li class="li2" >';
if(prov2[i][0]!=undefined&&prov2[i][0]!=null&&prov2[i][0]!=""){
var pro2vstr0="'"+prov2[i][0]+"'";
html+='<a href="#2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="GoToUrlItem('+pro2vstr0+');">'+prov2[i][0]+'</a>';
}else{
html+='';
}
if(prov2[i][1]!=undefined&&prov2[i][1]!=null&&prov2[i][1]!=""){
var prov2str1="'"+prov2[i][1]+"'";
html+='<a href="#2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="GoToUrlItem('+prov2str1+');">'+prov2[i][1]+'</a>';
}else{
html+='';
}
html+='</li>';
}
return html ;
}
感覺這樣寫好麻煩，不過最後還好弄出來了，如果有更好的方法請告訴我一下
頁面展示：
以上這篇java8 集合 多欄位 分組 統計個數程式碼就是小編分享給大家的全部內容了，希望能給大家一個參考，也希望大家多多支援我們。