java TreeUtil菜單遞歸工具類

第javaTreeUtil菜單遞歸工具類for(Menumenu:childList){

ListMenuchild=getChild(String.valueOf(menu.getId()),menus);

menu.setChildren(child);

//遞歸出口childList長度為0

if(childList.size()==0){

returnnewArrayList();

returnchildList;

}

上面這種遞歸，如果遇到大數(shù)據(jù)量，效率是極低的。比如前段時(shí)間剛實(shí)現(xiàn)了省市區(qū)鎮(zhèn)四層的樹結(jié)構(gòu)，面對5萬條的數(shù)據(jù)，竟然120s才遞歸完，這也太慢了，將來需求變成了省市區(qū)鎮(zhèn)鄉(xiāng)五層的結(jié)構(gòu)，那不就掛了？

大眼一看，不是跟上面的一樣嘛。仔細(xì)看it.remove();

假設(shè)有五萬的數(shù)據(jù)，根節(jié)點(diǎn)1萬，二級節(jié)點(diǎn)1萬，三級節(jié)點(diǎn)1萬，4級節(jié)點(diǎn)2萬。如果按照上面的邏輯走，每次都要從5萬中數(shù)據(jù)遞歸查找；而下面的邏輯是找到N級節(jié)點(diǎn)并且在總list中刪除。假設(shè)找到根節(jié)點(diǎn)的1萬數(shù)據(jù)，并且把他們從總list中刪除，總list剩4萬條數(shù)據(jù)，依次這樣，到了找4級節(jié)點(diǎn)時(shí)，總list就已經(jīng)剩2萬條數(shù)據(jù)了，總數(shù)據(jù)量從5萬變成了2萬，循環(huán)次數(shù)就少了，效率也就高了

importcom.energy.service.vo.RegionTree;

importjava.util.ArrayList;

importjava.util.Iterator;

importjava.util.List;

*@authorm

*@date2025/4/2

publicclassTreeUtil{

*創(chuàng)建樹結(jié)構(gòu)

*@paramregionTrees

*@return

privateListRegionTreetree(ListRegionTreeregionTrees){

//返回的節(jié)點(diǎn)樹

ListRegionTreerootNodes=newArrayList();

IteratorRegionTreeit=regionTrees.iterator();

while(it.hasNext()){

RegionTreenext=it.next();

//parent（上級Id）為0的是根節(jié)點(diǎn)

if("0".equals(next.getParentId())){

rootNodes.add(next);

it.remove();

//遍歷，找到二級節(jié)點(diǎn)

for(RegionTreeregionTree:rootNodes){

ListRegionTreechild=getChild(regionTrees,regionTree.getId().toString());

regionTree.setChildren(child);

returnrootNodes;

*查子節(jié)點(diǎn)

*@paramregions

*@paramparentId

*@return

privateListRegionTreegetChild(ListRegionTreeregions,StringparentId){

//子節(jié)點(diǎn)列表

ListRegionTreechildList=newArrayList();

IteratorRegionTreeit=regions.iterator();

while(it.hasNext()){

RegionTreeregionTree=it.next();

if(parentId.equals(regionTree.getParentId())){

childList.add(regionTree);

it.remove();

//遍歷遞歸獲取子節(jié)點(diǎn)的子節(jié)點(diǎn)

for(RegionTreeregionTree:childList){

ListRegionTreechild=getChild(regions,regionTree.getId().toString());

regionTree.setChildren(child);

//遞歸出口childList長度為0

if(childList.si