One option would be to add your DBTreeNode List as a member of BST Node along with other fields like Left, Right, etc... Then add accessors (getter, setter) for DBTreeNode. Hope this helps. Good Luck!
Here is an Example:
public class BST<Key extends Comparable<Key>, Value> {
private Node root; // root of BST
private class Node {
private Key key; // sorted by key
private Value val; // associated data
private Node left, right; // left and right subtrees
private int N; // number of nodes in subtree
private DBTreeNode VehicleDetails; // your list
public Node(Key key, Value val, int N) {
this.key = key;
this.val = val;
this.N = N;
this.VehicleDetails = new DBTreeNode(); // initialize your list
}
public DBTreeNode getDetails(){
return this.VehicleDetails;
}
public void addDetails(DBTreeNode details){
for(DBTreeNodeElement detail : details) this.VehicleDetails.add(detail);
}
}