Multi-level tree structure in Groovy -

using database table want create collection type output in groovy.

def categorylist =new hashmap();//to hold final result def parents=new hashmap(); def childs1= new arraylist(); def childs2= new hashmap(); def childs3= new arraylist(); list catlist =testing.executequery("from testing orgid in(:test)",['test':oid]) catlist.each{     if(it.parent==0){         def m=new hashmap();         m.put('id',it.id)         m.put('title',it.name)         def al =new arraylist()         m.put('children',al)         categorylist.put(it.id,m);         parents.put(it.id,it)     }else{         childs1.add(it)     } }  childs1.each{     def par = parents.get(it.parent)     if(par){         childs2.put(it.id,it)     }else{         childs3.add(it)     } } def reg = new hashmap();/*to hold sub trees merging childs3 main childs2*/ childs3.each{     def par = childs2.get(it.parent)     if(par){         if(!reg.get(par.id)){             map m = new hashmap()             m.put('id',par.id)             m.put('title',par.name)             def al =new arraylist()             al.add([id:it.id,title:it.name,parent:it.parent])             m.put('children',al)             reg.put(par.id,m);         }else{             reg.get(par.id).get('children').add([id:it.id,title:it.name,parent:it.parent])         }      } } /*merging sub trees main tree */ childs2.values().each{     def par = categorylist.get(it.parent)     if(par){         if(reg.get(it.id)){             par.get('children').add(reg.get(it.id))         }else{             par.get('children').add([id:it.id,title:it.name,parent:it.parent]) }     } }   def finallist = new arraylist(categorylist.values());    }  } 

i can able create tree upto 3 level.but want add 1 more subtree level.database having id,tilte , parent fields. can me solve problem..?