Solved

HashMaps and parent/child relationships

Posted on 2002-04-30
3
969 Views
Last Modified: 2012-05-04
I need to create a parent to child relationship of my records and would like to use hashmaps to store the data and then a TreeSet/Iterator to get the ordered value

The records are as follows and come in random order:

Record 1: Parent 1; Child 2
Record 2: Parent 2; Child 1
Record 3: Parent 1; Child 1
Record 4: Parent 3; Child 1

The output i'm trying to accomplish is:

Parent 1
     Child 1
     Child 2
Parent 2
     Child 1
Parent 3
     Child 1


I can easily fill the hash maps but can't figure out how to relate the children.

Thanks in advance.  Let me know if more clarification is needed.

Dave
 
0
Comment
Question by:mred_mred
  • 2
3 Comments
 
LVL 7

Accepted Solution

by:
yoren earned 75 total points
ID: 6982462
One way to do this would be to create a hashmap of {Parent} --> {SortedSet of children}. You can also have a separate SortedSet of parents or even store them in the hashmap. Here's how you'd add a child:

SortedSet parents = (SortedSet) map.get("root");
Parent p1 = (Parent) parents.first();
SortedSet children = (SortedSet) map.get(p1);
if (children == null) {
  children = new TreeSet();
  map.put(p1,children);
}
children.add(new Child("Child 1"));

To get your output, just iterate through the parents; for each parent, iterate through the SortedSet of children.

Alternatively, and especially if you need more than one level of parent to child relationships, consider creating a Node class which has as a field a SortedSet of children.

0
 

Author Comment

by:mred_mred
ID: 6983835
this definitely answered my question and i did seem to figure it out while waiting.  thanks for the quick response.

i do have more than one level.  where do i find the node class?  or do i create this my self?  class.child_node or something?  or is this a java class that i can use.

thanks
0
 
LVL 7

Expert Comment

by:yoren
ID: 6983902
No, you'd have to create the Node class yourself. A Node could be a parent or a child, depending on if it has any children. Of course, this is assuming that parents and children have basically the same information. In the Node class you'll probably want a "name" field, a "children" field (which would be a SortedSet of other Nodes), and any other information pertinent to a node.
0

Featured Post

Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
eclipse argument 14 61
Java DateChooser? 3 36
egit plugin on eclipse 8 64
Way to decrease size of apk file 9 70
For customizing the look of your lightweight component and making it look lucid like it was made of glass. Or: how to make your component more Apple-ish ;) This tip assumes your component to be of rectangular shape and completely opaque. (COD…
Java Flight Recorder and Java Mission Control together create a complete tool chain to continuously collect low level and detailed runtime information enabling after-the-fact incident analysis. Java Flight Recorder is a profiling and event collectio…
Viewers will learn about arithmetic and Boolean expressions in Java and the logical operators used to create Boolean expressions. We will cover the symbols used for arithmetic expressions and define each logical operator and how to use them in Boole…
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question