java - Algorithm for sorting a "plain-list-tree-structure" -

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sorry subject, didn't find better title :-)

i have tree structure, here's "node" class: 

public class categoria implements serializable {      private static final long serialversionuid = 1l;      @id     @generatedvalue(strategy = generationtype.identity)     private long id;      @notnull     private string name;      @onetomany(cascade=cascadetype.all,fetch=fetchtype.eager)     @joincolumn(name = "parent_id")     private list<categoria> children = new linkedlist<categoria>();      @manytoone(fetch=fetchtype.lazy)     @joincolumn(         name = "parent_id",         insertable=false,         updatable=false     )     private categoria parent;      @transient     private integer depth;      private integer ordernumber;  ... getters, setters, .... }

don't care hibernate/jpa annotations, there's no problem them, think of ideal pojo world.

i made recursive method builds "plain" list of adjacent nodes. so, imagine tree:

grandfather   |_ father      |_ son1      |_ son2   |_ uncle  grandmother   |_ mother

we have resulting list 1 (number "depth"): - grandfather (1) - father (2) - son1 (3) - son2 (3) - uncle (2) - grandmother (1) - mother (2)

all works good.

now want let users edit nodes sorting (between same depth nodes), mean: if want "son2" before "son1" in above list?

so tought add "ordernumber" property: ordernumbers 0 initially. user set son1's ordernumber 99 , son2's ordernumber 88.

the question is: how can rearrange resulting list sorting based on ordernumber?

but wait.... want sort "sublists", sons sorting absolutely not related "fathers" , "uncles" sorting!

thank helping us.

edit: you're missing 1 thing. did not explain myself well. here's example:

  • grandfather (depth:1, ordernumber:1)
  • father (depth:2, ordernumber:1)
  • son1 (depth:3, ordernumber:1)
  • son2 (depth:3, ordernumber:2)
  • uncle (depth:2, ordernumber:2)
  • grandmother (depth:1, ordernumber:2)
  • mother (depth:2, ordernumber:1)

now want swap son1 , son2 resulting list be:

  • grandfather (depth:1, ordernumber:1)
  • father (depth:2, ordernumber:1)
  • son2 (depth:3, ordernumber:1)
  • son1 (depth:3, ordernumber:2)
  • uncle (depth:2, ordernumber:2)
  • grandmother (depth:1, ordernumber:2)
  • mother (depth:2, ordernumber:1)

how can implement sort / compareto such purpose??

let categoria implement comparable. create custom compareto implementation, order depth , on ties additional ordernumber attribute decides. work in sortable collection.

but depending on problem solving tree-structure may more suitable implement custom iterator tree instead of recursively creating "list snapshots" ?


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