Java algorithm practices classify elements in a list by attributes into a tree-like map__java--other

Java algorithm practice, but also a useful tool class.
For example: A student Information list, the student's information by class, gender, school number, etc., will list according to class, gender classification.
Just:
Map map = Collectiontools.classifylist (studentalllist,
"ClassId", "sex");

This tool uses reflection to classify each student in the list into a tree map according to ClassID and sex.

Package utils;
Import java.lang.reflect.InvocationTargetException;
Import java.util.ArrayList;
Import Java.util.LinkedHashMap;
Import java.util.List;
 
Import Java.util.Map;
Import Org.apache.commons.beanutils.PropertyUtils; /** * * @author Klguang * @version 0.1/public class Collectiontools {/** * use Propertyutils to get the value of the bean, and root
     According to KeyName classified * @param list * List beans * @param keyname * Name of the bean that needs to be categorized * @return linkedhashmap<string, List&gt, map<br> in order the key of the map is the property name + "#" of the bean that needs to be sorted and the corresponding attribute value: Eg: "CLA ss#312 "<br> * value is list<bean><br> * * @throws illegalaccessexception * @th Rows InvocationTargetException * @throws nosuchmethodexception * * public static linkedhashmap<string, L Ist> Classify (list list, String KeyName) throws Illegalaccessexception, InvocationTargetException, Nosuchme thodexception {linkedhashmap<String, list> target = new Linkedhashmap (); For (object obj:list) {//Get the value of the property (KeyName) that the bean needs to categorize, do not type convert Object Okeyvalue = PROPERTYUTILS.GETP
            Roperty (obj, keyname);
            String keyvalue = KeyName + "#" + string.valueof (okeyvalue);  if (!target.containskey (keyvalue)) {//If there is no collation key value in the map, add the key value and the corresponding list ArrayList keylist =
                New ArrayList ();
                Keylist.add (obj);
            Target.put (KeyValue, keylist); else {//If there is a collation key value, add the bean ArrayList keylist = (ArrayList) target.get in the appropriate list (Keyval
                UE);
            Keylist.add (obj);
    } return target; /** * * Will classify the map<string, list> according to KeyName classification, and the index control recursion.
     <br> * Because the direct call is meaningless, this method is private, * * @param MOCL * Map of Classified list<br> * The Application Method <br> * linkedhashmap<
     String, list> classify (list list, String * keyname) <br> * classify List as map<br>            * * @param index * with conditions index < Keynames.length control recursion * * @param keynames *
     The property name of the bean that needs to be categorized * @return * @throws illegalaccessexception * @throws invocationtargetexception * @throws nosuchmethodexception * * private static linkedhashmap<string, map> classify (map<string, List
            > mocl, int index, String ... keynames) throws Illegalaccessexception, InvocationTargetException,
        nosuchmethodexception {//Single Step Understanding: Target is a function parameter map<string, list> Mocl again categorized as linkedhashmap<string,map>
        Recursion to the end this is the final categorized Map linkedhashmap<string, map> target = new Linkedhashmap ();
        Control the recursive condition, the starting index should always be 1. if (Index < keynames.length) {//swap is used to hold the value of the parameter index, this is one of the most error-prone places//guarantees: In the parameter map<string, List > MoThe CL layer loops with the same index parameter value.
            int swap = index;
                For (map.entry<string, list> entry:mocl.entrySet ()) {String Mocl_key = Entry.getkey ();
                List mocl_list = Entry.getvalue ();
                The list<bean> is reclassified again linkedhashmap<string, list> _MOCL = classify (mocl_list, Keynames[index]);
                    If index reaches the last of the array, it must be list<bean> to map, recursive End if (index = = keynames.length-1) {
                Target.put (Mocl_key, _MOCL);
                    else {//_MOCL list<bean> to map, reclassified//_MOCM as the abbreviation for map of classified map
                    linkedhashmap<string, map> _mocm = classify (_MOCL, ++index, keynames);
                Target.put (Mocl_key, _MOCM);
            index = swap;
    } return target; /** * will map<string, list> map is categorized according to the property name KeyName The bean needs to categorize * @Map * @param keyname * param map * Map of Classified list<br> * List  The property name of the bean that needs to be categorized * @return * @throws illegalaccessexception * @throws invocationtargetexception * @throws nosuchmethodexception * * public static linkedhashmap<string, map> Classifymap (map<string, Lis
        t> map, String KeyName) throws Illegalaccessexception, InvocationTargetException, nosuchmethodexception {
        linkedhashmap<string, map> target = new Linkedhashmap ();
            For (map.entry<string, list> entry:map.entrySet ()) {List map_list = Entry.getvalue ();
            String Map_key = Entry.getkey ();
            linkedhashmap<string, list> keymap = classify (map_list, keyname);
        Target.put (Map_key, keymap);
    return target; /** * Classifies list<bean> according to the properties of the specified bean, and the keynames order affects the collation results. <br> * Eg: A student list, categorized according to class and sex &LT;BR&GT            * Map map = collectionutils.classifylist (studentlist, "classId", "Sex");<br> * * @param list *         List Beans * @param keynames * Array contains the name of the property of the bean that needs to be categorized * @return sorted tree map<br> * The key of the map is the property name + "#" + corresponding property value for the bean that needs to be categorized: eg: "class#312" <br> * Map has a value of list or map * * @th Rows illegalaccessexception * @throws invocationtargetexception * @throws nosuchmethodexception * * Publ IC Static Linkedhashmap classifylist (List list, String ... keynames) throws Illegalaccessexception, Invocationt
        Argetexception, Nosuchmethodexception {if (keynames = null | | | keynames.length = = 0) return null;
        if (keynames.length = = 1) return classify (list, keynames[0]);
    else return classify (classify (list, keynames[0]), 1, keynames); }
}

Package test;
Import java.lang.reflect.InvocationTargetException;
Import java.util.ArrayList;
Import Java.util.HashMap;
Import Java.util.Iterator;
Import java.util.List;
 
Import Java.util.Map; Import Utils.
Collectiontools; Import Utils.
 
Jsonutil; public class Collectionclassifytest {/** * @param args * @throws nosuchmethodexception * @throws INV Ocationtargetexception * @throws illegalaccessexception */public static void main (string[] args) throws Ill Egalaccessexception, InvocationTargetException, nosuchmethodexception {//TODO auto-generated method Stub list<student> studentalllist = new ArrayList ()//So Class of students Studentalllist.add (new Student ("1
        "," A ", 1," Ⅰ "," North "," 1 "));
        Studentalllist.add (New Student ("2", "C", 1, "Ⅱ", "Upper", "0"));
        Studentalllist.add (New Student ("3", "C", 1, "Ⅰ", "North", "1"));
        Studentalllist.add (New Student ("4", "B", 1, "Ⅰ", "Wide", "1")); Studentalllist.add(New Student ("5", "A", 1, "Ⅳ", "Guang", "1"));
        Studentalllist.add (New Student ("6", "C", 1, "Ⅳ", "Upper", "0"));
        Studentalllist.add (New Student ("7", "A", 1, "Ⅳ", "Wide", "0"));
        Studentalllist.add (New Student ("8", "B", 1, "Ⅰ", "Wide", "0"));
        Studentalllist.add (New Student ("8", "D", 1, "Ⅲ", "North", "0"));
        Studentalllist.add (New Student ("8", "D", 1, "Ⅲ", "Wide", "0"));
 
         Studentalllist.add (New Student ("8", "D", 1, "Ⅲ", "Upper", "0"));
          
          
         Map map = collectiontools.classifylist (studentalllist, "classId", "sex");
         SYSTEM.OUT.PRINTLN (Jsonutil.tojson (map));
         
        Do contrast//system.out.println (Jsonutil.tojson (Classifytest (studentalllist)));
        Date Begin=new date (); for (int i = 0; i < 1000000 i++) {//Map map = Collectionutils.classifylist (studentalllist, "province", "a
Cademyid ",//" ClassId "," Team "," sex "); SYSTEM.OUT.PRINTLN (Jsonutil.tojson (map));
        }//date end=new Date ();
         
 
    System.out.println (End.gettime ()-begin.gettime ());  } static Map Classifytest (list<student> studentalllist) {//step 1 map<string, list> map =
        New hashmap<string, list> ();
        map<string, object> maplast = new hashmap<string, object> (); for (Student student:studentalllist) {for (Iterator it = Studentalllist.iterator (); It.hasnext ();)
 
            {Student Student = (Student) it.next (); if (Map.containskey (STUDENT.GETCLASSID)) {//If the array already exists, put it here List studentlist = Map.get (student.getcla
                SsId ());
            Studentlist.add (student);
                else {List studentlist = new ArrayList ();////re-declare an array List studentlist.add (student);
            Map.put (Student.getclassid (), studentlist);
 
        }//System.out.println (Jsonutil.tojson (map)); //Step 2//Use data grouped by processing 1 steps, GROUP by gender/female again for (map.entry<string, list> m:map.entryset ()) {//Key value traversal Map Map maplist = new HashMap (); List Studentsingle = M.getvalue (); Students of the same class, men and women List studentlistmen = new ArrayList (); Declare a store boy's list List studentlistwomen = new ArrayList (); Declare a girl's list for (iterator it = Studentsingle.iterator (); It.hasnext ();)
                {//traverse Student Student = (Student) it.next ();
                    if ("0". Equals (Student.getsex ())) {//male studentlistmen.add (student);//boy} else { Studentlistwomen.add (student);
            Girls} maplist.put ("female", studentlistwomen);
            Maplist.put ("Male", studentlistmen);
        Maplast.put (M.getkey (), maplist);
    return maplast; }
}

Package test;  /** * @author Klguang * */public class Student {private string StudentID;//School number private string sex;//Sex 0 men
    1 female private int team;
    Private String classId;
     
    private string academyid;//College private string Province;
        Public Student (String StudentID, String classId, String sex) {super ();
        This.studentid = StudentID;
        This.classid = classId;
    This.sex = sex;
        Student (String StudentID, String Classid,int team, string sex) {super ();
        This.studentid = StudentID;
        This.classid = classId;
        This.team=team;
    This.sex = sex;
        Student (String StudentID, String Classid,int team, string academyid,string sex) {super ();
        This.studentid = StudentID;
        This.classid = classId;
        This.team=team;
        This.sex = sex;
    This.academyid=academyid; Student (String StudentID, String Classid,int team, String Academyid,string province,string Sex) {super ();
        This.studentid = StudentID;
        This.classid = classId;
        This.team=team;
        This.sex = sex;
        This.academyid=academyid;
    This.province=province;
    Public String GetClassID () {return classId;
    } public void Setclassid (String classId) {this.classid = ClassId;
    Public String Getstudentid () {return studentid;
    } public void Setstudentid (String studentid) {this.studentid = StudentID;
    Public String Getsex () {return sex;
    } public void Setsex (String sex) {this.sex = sex;
    public int Getteam () {return team;
    public void Setteam (int team) {this.team = team;
    Public String Getacademyid () {return academyid;
    } public void Setacademyid (String academyid) {This.academyid = Academyid; Public String getprovince () {REturn Province;
    } public void Setprovince (String province) {this.province = province; }   
}

Package utils;
 
Import Java.util.Date;
Import Com.alibaba.fastjson.JSON;
Import Com.alibaba.fastjson.serializer.SerializeConfig;
Import Com.alibaba.fastjson.serializer.SerializerFeature;
 
Import Com.alibaba.fastjson.serializer.SimpleDateFormatSerializer;
    public class Jsonutil {private static serializeconfig mapping = new Serializeconfig ();
    private static String DateFormat;
    static {DateFormat = "yyyy-mm-dd HH:mm:ss"; public static String Tojson (Object jsontext) {return json.tojsonstring (Jsontext, serializer
    Feature.writedateusedateformat); public static string Tojson (string dateformat, Object jsontext) {mapping.put (Date.class, New Simpledatefo
        Rmatserializer (DateFormat));
    Return json.tojsonstring (jsontext, mapping); public static String Torealjson (Object jsontext) {return json.tojsonstring (jsontext,serializerfeature.
    Disablecircularreferencedetect); }
}

{"classid#a": {"sex#1": [{"Academyid": "Ⅰ", "classId": "A",
            "Province": "North", "Sex": "1", "StudentID": "1", "Team": 1 }, {"Academyid": "Ⅳ", "classId": "A", "province": "Wide
        "," Sex ":" 1 "," StudentID ":" 5 "," Team ": 1}], "Sex#0": [{"Academyid": "Ⅳ", "classId": "A", "Province": " 
    Wide "," Sex ":" 0 "," StudentID ":" 7 "," Team ": 1}]},
                "Classid#c": {"sex#0": [{"Academyid": "Ⅱ", "classId": "C",
            "Province": "On", "Sex": "0", "StudentID": "2", "Team": 1 },
            {
                "Academyid": "Ⅳ", "classId": "C", "Province": "Up", "sex":
            "0", "StudentID": "6", "Team": 1}], "sex#1": [ {"Academyid": "Ⅰ", "classId": "C", "Province": "North", "sex"
        : "1", "StudentID": "3", "Team": 1}]}, "classid#b": { "Sex#1": [{"Academyid": "Ⅰ", "classId": "B", "Province":
        "Guang", "Sex": "1", "StudentID": "4", "Team": 1}],  "Sex#0": [{"Academyid": "Ⅰ", "classId": "B", "Province":
    "Guang", "Sex": "0", "StudentID": "8", "Team": 1}]
  }, "classid#d": {      "Sex#0": [{"Academyid": "Ⅲ", "classId": "D", "Province
            ":" North "," Sex ":" 0 "," StudentID ":" 8 "," Team ": 1}, {"Academyid": "Ⅲ", "classId": "D", "province": "Wide", "sex ":" 0 "," StudentID ":" 8 "," Team ": 1}, {" Academyi D ":" Ⅲ "," ClassId ":" D "," Province ":" Up "," Sex ":" 0 "," Stu Dentid ":" 8 "," Team ": 1}]}}