How remove (or change) children inside a JTree

Question

hi,
I did a program where there are informations with a structure of dependence that should be showed inside JTree components.
I realized this purpose in my program .
But I am findind very difficult (after having put the information inside the JTre in the start) to show them again inside the JTrees when they are changed.
I don't know how to remove or change the informations after they are put on the children of the JTree using the methods that I found in the documentation to reach this purpose...
I need some help ...
To explain well my problem, and facilitate the helpers, I post some code that show my problem..
The program show a GUI with some JTrees.
The informations are contained in two strings, and in the GUI are also two buttons that can load the informations inside the JTree when they are clicked.
Thank you in advance
regards
tonyMrsangelo
public class JTree_TryToUseIt_ChangingNodes extends javax.swing.JFrame {
    private PanelFulViewConteiner jPanelFulViewConteiner;
    Dimension dimPrefArcPanels = new Dimension(910, 150);
    Dimension dimMinArcPanels = new Dimension(700, 100);
    Dimension dimPrefSemiArcPanels = new Dimension(850, 140);
    Dimension dimMinSemiArcPanels = new Dimension(550, 90);
    Dimension dimPrefBodyXpicPanels = new Dimension(900, 150);
    Dimension dimMinBodyXpicPanels = new Dimension(700, 150);
    Dimension treePrefDim = new Dimension(90, 110); //
    Dimension treeMinDim = new Dimension(60, 110);
    PanelToShowTrees panel_trees;
    public JTree_TryToUseIt_ChangingNodes() {
        getContentPane().setLayout(new GridBagLayout());
        GridBagConstraints gBC = new GridBagConstraints();
        jPanelFulViewConteiner = new PanelFulViewConteiner();
        gBC.gridx = 0;
        gBC.gridy = 0;
        gBC.gridwidth = 10;
        add(jPanelFulViewConteiner, new GridBagConstraints());
        gBC.gridx = 0;
        gBC.gridy = 1;
        gBC.gridwidth = 10;
        pack();
        panel_trees = this.jPanelFulViewConteiner.jPanelFulContainerTop.panelToShowTrees;
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocation(50, 50);
        setVisible(true);
    private void fillTrees(String[] strings) {
        collapseTrees();
        removeNodes();
        for (int index = 0; index < strings.length; index++) {
            DefaultMutableTreeNode dmt = new DefaultMutableTreeNode(strings[index]);
            String knotStr = strings[index].substring(0, 1);
            int knot = -1;
            try {
                knot = Integer.parseInt(knotStr);
            } catch (NumberFormatException e) {
            panel_trees.root_Node[knot].add(dmt);
            panel_trees.validate();
            panel_trees.repaint();
        collapseTrees();
    void collapseTrees() {
        for (int i = 0; i < 8; i++) {
            panel_trees.jTree.collapseRow(0);
panel_trees.jTree[i].expandRow(0);
panel_trees.validate();
panel_trees.repaint();
void removeNodes() {
for (int i = 0; i < 8; i++) {
panel_trees.jTree[i].removeAll();
panel_trees.validate();
panel_trees.repaint();
public static void main(String args[]) {
JTree_TryToUseIt_ChangingNodes xx = new JTree_TryToUseIt_ChangingNodes();
class PanelFulViewConteiner extends JPanel {
PanelFulContainerTop jPanelFulContainerTop;
PanelFulContainerBottom jPanelFulContainerBottom;
public PanelFulViewConteiner() {
GridBagLayout gbl = new GridBagLayout();
this.setLayout(gbl);
GridBagConstraints gBC = new GridBagConstraints();
jPanelFulContainerTop = new PanelFulContainerTop();
gBC.gridx = 0;
gBC.gridy = 0;
add(jPanelFulContainerTop, gBC);
jPanelFulContainerBottom = new PanelFulContainerBottom();
gBC.gridx = 0;
gBC.gridy = 2;
add(jPanelFulContainerBottom, gBC);
class PanelFulContainerTop extends JPanel {
PanelToShowTrees panelToShowTrees;
public PanelFulContainerTop() { // costruttore
this.setMinimumSize(dimMinArcPanels);
this.setPreferredSize(dimPrefArcPanels);
setLayout(new FlowLayout());
panelToShowTrees = new PanelToShowTrees();
add(panelToShowTrees);
}// costruttore
class PanelFulContainerBottom extends JPanel {
JButton but1 = new JButton("load string1");
JButton but2 = new JButton("load string2");
String[] str1 = {"0-AAA", "0-BBBBBB", "2-CCCCC", "2-DDDDDD", "2-EEEEEEE", "5-FFFFFF", "5-GGGGGG", "5-HHHHHH", "7-IIIIII", "7-KKKKKKK", "7-LLLLLL", "7-MMMMMM"};
String[] str2 = {"0-aaaaa", "0-bbbbb", "0-cccc", "2-ddddd", "2-eeee", "3-ffffff", "3-gggggg", "3-hhhhh", "4-iiiiii", "4-kkkkk", "7-lllllll", "7-mmmmm", "7-nnnnn"};
public PanelFulContainerBottom() {// costruttore
this.setMinimumSize(dimMinArcPanels);
this.setPreferredSize(dimPrefArcPanels);
add(but1);
but1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
fillTrees(str1);
add(but2);
but2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
fillTrees(str2);
class PanelToShowTrees extends JPanel {
JScrollPane jScrollPane[];
JTree jTree[];
DefaultMutableTreeNode[] root_Node;
public PanelToShowTrees() {
this.setMinimumSize(dimMinSemiArcPanels);
this.setPreferredSize(dimPrefSemiArcPanels);
setLayout(new FlowLayout());
jScrollPane = new JScrollPane[8];
jTree = new JTree[8];
root_Node = new DefaultMutableTreeNode[8];
for (int i = 0; i < 8; i++) {
root_Node[i] = new DefaultMutableTreeNode(" " + (8 - i));
jTree[i] = new JTree(root_Node[i]);
jScrollPane[i] = new JScrollPane();
jScrollPane[i].setViewportView(jTree[i]);
add(jScrollPane[i]);
jScrollPane[i].setPreferredSize(treePrefDim);
jScrollPane[i].setMinimumSize(treeMinDim);
jTree[i].addTreeSelectionListener(new TreeSelectionListener() {
public void valueChanged(TreeSelectionEvent e) {
showContentOfTheTree(e);
private void showContentOfTheTree(TreeSelectionEvent e) {
String stringaGotFromEvent = e.getPath().toString();
JOptionPane.showMessageDialog(rootPane, "found =---> " + stringaGotFromEvent);

Answer 1

hi Andre,
thank you for answering me.
I have not much practice with JTrees so I find some difficulty to use it...
After I got your advice, I made changed a little the design of my program..
This it is a program for management of a dentist office, and I would show in 8 JTrees (every jTree root represents the teeth in a dental arch) the treatments that each tooth got.
How I said, the 8 JTree roots are representing the teeth, and in this architecture the problem is:
- to add a node to a tree root to indicate a treatment for that tooth;
- to delete all the children from a jTree root before beginning to add new child, before writing again treatments, when the informations are changed.
Following your help, I made this two functions to reach this purpose:
private void assingTreatmentToTooth(int toothNmbr, String strTreatment) {
        DefaultMutableTreeNode newChild = new DefaultMutableTreeNode(strTreatment); // new treatment to add
        DefaultTreeModel model = (DefaultTreeModel) panel_trees.jTreeXdentalRoots[toothNmbr].getModel(); // get model for the root Tree
        DefaultMutableTreeNode parentNode = (DefaultMutableTreeNode) model.getRoot();
        model.insertNodeInto(newChild, parentNode, 0); // always assign 0 as first node
    } // assingTreatmentToTooth()
private void removeTreatmentFromAtooth(int toothNmbr, int childNmbr) {
        DefaultTreeModel model = (DefaultTreeModel) panel_trees.jTreeXdentalRoots[toothNmbr].getModel();  // get model for the root Tree
        DefaultMutableTreeNode child = (DefaultMutableTreeNode) model.getChild(model, childNmbr);
        model.removeNodeFromParent(child);
    } // removeTreatmentToTooth()when the second function is executed, I get this error:
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: javax.swing.tree.DefaultTreeModel cannot be cast to javax.swing.tree.TreeNode
at the line : DefaultMutableTreeNode child = (DefaultMutableTreeNode) model.getChild(model, childNmbr);
DefaultMutableTreeNode child = (DefaultMutableTreeNode) model.getChild(model, childNmbr);
could you tell me what is wrong ?
regards
TonyMrsangelo