How to implement a tree data-structure in Java?

Question

Is there any standard Java library class to represent a tree in Java?

Specifically I need to represent the following:

• The sub-tree at any node can have

Answer 1

I wrote a small "TreeMap" class based on "HashMap" that supports adding paths:

import java.util.HashMap;
import java.util.LinkedList;

public class TreeMap extends LinkedHashMap> {

    public void put(T[] path) {
        LinkedList list = new LinkedList<>();
        for (T key : path) {
            list.add(key);
        }
        return put(list);
    }

    public void put(LinkedList path) {
        if (path.isEmpty()) {
            return;
        }
        T key = path.removeFirst();
        TreeMap val = get(key);
        if (val == null) {
            val = new TreeMap<>();
            put(key, val);
        }
        val.put(path);
    }

}

It can be use to store a Tree of things of type "T" (generic), but does not (yet) support storing extra data in it's nodes. If you have a file like this:

root, child 1
root, child 1, child 1a
root, child 1, child 1b
root, child 2
root, child 3, child 3a

Then you can make it a tree by executing:

TreeMap root = new TreeMap<>();
Scanner scanner = new Scanner(new File("input.txt"));
while (scanner.hasNextLine()) {
  root.put(scanner.nextLine().split(", "));
}

And you will get a nice tree. It should be easy to adapt to your needs.