java8 集合多字段分组统计个数代码

2023-07-17 23:51:03 174

packagecom.demo.dto; publicclassUser{ privateIntegerid; privateStringuserName; privateStringpassword; privateIntegerage; privatelongc; publicUser(){ super(); //TODOAuto-generatedconstructorstub } publicUser(Integerid,StringuserName,Stringpassword,Integerage){ super(); this.id=id; this.userName=userName; this.password=password; this.age=age; } publicIntegergetId(){ returnid; } publicvoidsetId(Integerid){ this.id=id; } publicStringgetUserName(){ returnuserName; } publicvoidsetUserName(StringuserName){ this.userName=userName==null?null:userName.trim(); } publicStringgetPassword(){ returnpassword; } publicvoidsetPassword(Stringpassword){ this.password=password==null?null:password.trim(); } publicIntegergetAge(){ returnage; } publicvoidsetAge(Integerage){ this.age=age; } publiclonggetC(){ returnc; } publicvoidsetC(longl){ this.c=l; } @Override publicStringtoString(){ return"User[id="+id+",userName="+userName+",password="+password+",age="+age+",c="+c +"]"; } publicstaticvoidmain(String[]args){ Useru1=newUser(1,"aa","aap",23); Useru2=newUser(2,"aa","aap",23); Useru3=newUser(3,"bb","aap",23); Useru4=newUser(4,"cc","aap",23); Useru5=newUser(5,"cc","aap",23); Useru6=newUser(6,"cc","aap",23); Useru7=newUser(7,"aa","aap",24); Listlist=newArrayList(); 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>map=list.stream().collect(Collectors.groupingBy(User::getUserName,Collectors.groupingBy(User::getAge,Collectors.counting()))); //jdk8以下: Map>map=newHashMap>(); for(Useruser1:list){ Mapvalue=newHashMap(); longcount=0; if(map.containsKey(user1.getUserName())){ continue; } for(inti=0;i{ System.out.println(k+">>>>"+v); }); Listlist2=newArrayList(); list.forEach(user->{ map.forEach((k,v)->{ if(k==user.getUserName()){ Longremove=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); }); } }

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]

publicMapcampus_list_provence(HttpServletRequestrequest,HttpServletResponseresponse)throwsException{ Mapmap=newHashMap(); Stringsql="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"; Listlist=bd.getSQLList(sql); //创建第一个list1，里面存入省份名称少于4个字的 Listlist1=newArrayList(); //创建第二个list2，里面存入省份名称大于4个字的 Listlist2=newArrayList(); if(list!=null&&list.size()>0){ for(Stringstring:list){ if(string.length()>4){ list2.add(string); }else{ list1.add(string); } } } intkeyToken=0; inttoIndex=3; List

java8 集合 多字段 分组 统计个数代码

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java8 集合多字段分组统计个数代码