JTable + Hashtable + Collection doesn't seem to work properly

Question

Hi folks,
I'm having a problem with JTree class. Basically, I want to instantiate it by using an Hashtable, though
depending on the fact that I use collection or arrays the result can substantially vary.
Take the following use case:
import javax.swing.*;
import java.util.*;
public class Tree extends JApplet{
  public Tree(){
    super();
    setSize(300, 250);
    init();
    setVisible(true);
  public void init(){
    Hashtable<String,List<String>> hash = new Hashtable<String,List<String>>();
    hash.put("Foo", Arrays.asList("Bar"));
    JTree tree = new JTree(hash);
    getContentPane().add(tree);
}This displays a wrong tree, in fact you should have a Foo node that contains a Bar leaf.
Now if I use array instead of collections (generics are not the problem) everything work just as
expected!?
import javax.swing.*;
import java.util.*;
public class Tree extends JApplet{
  public Tree(){
    super();
    setSize(300, 250);
    init();
    setVisible(true);
  public void init(){
    Hashtable<String,String [] > hash = new Hashtable<String,String []>();
    hash.put("Foo", new String []{"Bar"});
    JTree tree = new JTree(hash);
    getContentPane().add(tree);
}Considering that the constructor of JTree allows the following instantiation for Hastable:
public JTree(Hashtable<?,?> value)the use of wildcards let me assume that I can put whatever I like as the type of my keys/values.
Am I missing something or this is indeed some very strange (buggy) behavior.
Cheers,
Mirco

Answer 1

lins314159 wrote:
[Javadocs for createChildren method|http://java.sun.com/javase/6/docs/api/javax/swing/JTree.DynamicUtilTreeNode.html#createChildren%28javax.swing.tree.DefaultMutableTreeNode,%20java.lang.Object%29]
If you look in the source code for JTree, there's no mention of Lists in there. Not quite sure why they handle Vectors and Hashtables only instead of Lists and Maps.Hi lins,
thanks for taking the time for giving me your though.
I have take a glance at the javadoc for method createChildren, but once again it tells me that if I have an entry of the type
<A,Collection<B>> I should get a Node named after the object of type A and whose leaf are the ones contained in the collection.
I agree with you that is bizarre that the JTree constructor only accept Hashtable (and not Map, that appear to me more convenient);
but I can live with that as long as the value field of the hashtable behave as I would expect.
I'm not an experienced Java programmer, so if any of you gurus has any thoughts on that, please let me know.
Cheers,
Mirco
Edited by: Mirco on Feb 29, 2008 12:07 AM