Void method to jTextArea-Transform console(recursive method) output to jTextArea

Question

I have the following code

class BinaryTree{
Node root;
        public void inOrderTraverseTree(Node node) {

            if (node!= null) {

                // Traverse the left node

                inOrderTraverseTree(node.leftChild);

                // Visit the currently focused on node

                System.out.println(node);

                // Traverse the right node

                inOrderTraverseTree(node.rightChild);

            }

        }

        public void preorderTraverseTree(Node node) {

            if (node!= null) {

                System.out.println(node);

                preorderTraverseTree(node.leftChild);
                preorderTraverseTree(node.rightChild);

            }

        }
    public static void main(String[] args) throws SQLException {

            BinaryTree theTree = new BinaryTree();
          //retrieve data from database, create tree, call functions, everything //works-It shows well at console
          theTree.preorderTraverseTree(theTree.root);
          theTree.inOrderTraverseTree(theTree.root);

    }

and the second class

class Node{
Node leftChild;
    Node rightChild;

    Node(int id,int search,int left,int right,String name) {
                this.left=left;
                this.right=right;
        this.id = id;
                this.search=search;
        this.name = name;


        }

//get and sett methods

}

Which is my problem. Well console application works.I get input from DATABASE USING JDBC. The inorder, preorder... shows well, verified by paper. My problem is: -I can not print results in a jTextArea from a void method.

What I have tried to do:

• Print the results with writeObject to a file and the show them in jTextArea(fail)
• Try to convert to String (fail)
• transform void method to a string one(returning null-fail again).I guess it is recursive and I don`t do it OK

Any tips? How can I print the result of this method "theTree.preorderTraverseTree(theTree.root)" into a jTextArea?

Edit: I did declare a String/Object and tried to parse the value from the method into it, but without succes. Also I don't know why inside a void method setText method is not working.

public void preorderTraverseTree(Node node) {

        if (node != null) {


            System.out.println(node);
                          jTextArea1.setText(node.toString());

            preorderTraverseTree(node.leftChild);
            preorderTraverseTree(node.rightChild);

        } 
    }        

//and the button

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {          
Node theTree;
theTree.preorderTraverseTree(theTree.root);
}

My question: Inside the preorderTraverseTree, why .setTextMethod doesn't work.

Why do I need this? Well, I wont console output to be in a jTextArea