(original) Parent-child relationship data is processed recursively into tree data (reduces database pressure)

Package Test;import Java.util.arraylist;import java.util.hashmap;import java.util.linkedlist;import java.util.List; Import java.util.map;/** * idpiddatastotree<br> * &LT;P&GT;AUTHOR:TD </P> * <p>date:2016 Year September 30 pm 4: 54:59</p> * &LT;P&GT;DESC: Processing the subordinate data into a tree data structure </P> * @param response * @param request */public class Idpiddat astotree {public static void main (string[] args) {List < Map < String, Object >> list = new Arrayl        ist < Map < String, Object >> ();        Map < String, Object > m = null;            for (int i = 1; i < i++) {m = new HashMap < String, Object > ();            M.put ("id", i + "");            M.put ("name", "I am node" + i);            M.put ("ParentID", I-1 + "");        List.add (m); List < Map < String, object >> treemenulist = new LinkedList < Map < String, Object >> ()        ;   Treemenulist = treemenulist (list, treemenulist, "0");     SYSTEM.OUT.PRINTLN ("The data to be processed is:" + list.tostring ());    System.out.println ("Well-processed tree-like structure:" + treemenulist.tostring ());     }/** * * @param menulist raw data * @param treemenulist Tree Data Object * @param the parent ID of the parentid data * @return */@SuppressWarnings ("unchecked") public static List < Map < String, Object >> treemenulist (list &lt ;        Map < String, object >> list, List < Map < String, object >> treemenulist, String parentid) {            If no root node is in the case ("0". Equals (ParentID)) {treemenulist = Getchildnodelist ("0", list);                For (Map < string, Object > Treemenu:treemenulist) {String id = (string) treemenu.get ("id");                Treemenu.put ("Childnode", Getchildnodelist (ID, list));            Treemenulist (list, treemenulist, id); }} else {for (Map < String, Object > Treemenu:treemenulist) {//To determine if there are child elements, some words recursive child              The vegetarian continues to judge  String id = (string) treemenu.get ("id"); if (Treemenu.containskey ("Childnode")) {//Get child elements List < Map < String, Object &                    Gt;> childnodelist = (List < Map < String, Object >>) treemenu.get ("Childnode"); if (childnodelist! = null && childnodelist.size () > 0) {for (Map < String, Object &G T                        Tmenu:childnodelist) {treemenulist (list, childnodelist, tmenu.get ("id"). toString ());                    }}//If there are no child elements, query according to ID son assigns son to value} else {                    List < Map < String, Object >> chlist = getchildnodelist (ID, list);                        if (null! = chlist) {treemenu.put ("Childnode", chlist);                    Treemenulist (list, chlist, id);    }}}} return treemenulist; }    /** * * * @param parentid Data Parent ID * @param list raw Data * @return */public static List < Map < Stri Ng, Object >> getchildnodelist (String parentid, List < Map < String, object >> list) {List <        Map < String, object >> childnodelist = new LinkedList < Map < String, object >> (); For (Map < String, Object > Childnode:list) {//New New object (if you do not re-new the object, the value of list will change, do not know what happens?)            ) Map < String, object > m = new HashMap < String, object > ();            M.putall (Childnode);            String pId = (string) childnode.get ("ParentID");            if (Pid.equals (ParentID)) {Childnodelist.add (M);        }} if (childnodelist.size () = = 0) return null;    return childnodelist; }}

　　

(original) Parent-child relationship data is processed recursively into tree data (reduces database pressure)