java8 集合 多字段 分组 统计个数代码
1.user实体
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, "aa", "aap", 23);
User u3=new User(3, "bb", "aap", 23);
User u4=new User(4, "cc", "aap", 23);
User u5=new User(5, "cc", "aap", 23);
User u6=new User(6, "cc", "aap", 23);
User u7=new User(7, "aa", "aap", 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(根据第二个字段:userName和第四个字段:age 统计重复的记录数)
//jdk8的方法统计个数:
Map<String, Map<Integer, Long>> map = list.stream().collect(Collectors.groupingBy(User::getUserName,Collectors.groupingBy(User::getAge,Collectors.counting())));
//jdk8以下:
Map<String,Map<Integer,Long>> map=new HashMap<String,Map<Integer,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);
});
//遍历最后想要的结果(User中c为统计后的个数，方便前台遍历集合时单元格合并行)
list2.forEach(u ->{
System.out.println(u);
});
}
}
备注：运行结果如下
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, userName=aa, password=aap, age=23, c=0]
User [id=7, userName=aa, password=aap, age=24, c=1]
User [id=3, userName=bb, password=aap, age=23, c=1]
User [id=4, userName=cc, password=aap, age=23, c=3]
User [id=5, userName=cc, password=aap, age=23, c=0]
User [id=6, userName=cc, password=aap, age=23, c=0]
此处是为了实现如下效果：
补充知识：List集合中元素按照固定数量进行分组
最近做项目，被要求将全国所有省份在页面中展示出来，但是要求
1、字少的三个省份占一行
2、字多的两个省份占一行
想来想去只能想到查询出所有省份，然后分组返回数据，上代码
public Map<String,Object> campus_list_provence(HttpServletRequest request,HttpServletResponse response)throws Exception{
Map<String,Object> map=new HashMap<String,Object>();
String sql="查询所有省份的名称，可以先在数据库中将全国所有省份建一个表";
List<String> list=bd.getSQLList(sql);
//创建第一个list1，里面存入省份名称少于4个字的
List<String> list1=new ArrayList<String>();
//创建第二个list2，里面存入省份名称大于4个字的
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()){ //作用为toIndex最后没有3条数据则剩余几条newList中就装几条
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()){ //作用为toIndex最后没有2条数据则剩余几条newList中就装几条
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;
}
页面接收
function campus_list_ByProvence(req_data){
$.ajax({
type : "POST",
url : "刚才方法的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失败！");}
});
}
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 ;
}
感觉这样写好麻烦，不过最后还好弄出来了，如果有更好的方法请告诉我一下
页面展示：
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