NetBeansでGUIを作成しています。

　まず紹介されているコードは動きませんし，方向性も余りよろしくないのではないかと。元のコードの意図が良く分からないので外しているかも知れませんが，データを保持するモデルを用意してやって，データ更新時にフォーム側へ通知が届く様にしてやるのが良いのではないでしょうか。

import java.util.Observable;
import java.util.Observer;

public class Hatena extends javax.swing.JFrame implements Observer {

    LabelModel model;
    HatenaTest delegate;

    private void setModel(LabelModel newModel) { this.model = newModel; }
    private LabelModel getModel() { return this.model; }
    private void setDelegate(HatenaTest newDelegate) { this.delegate = newDelegate; }
    private HatenaTest getDelegate() { return this.delegate; }

    /** Creates new form Hatena */
    public Hatena() {
        initComponents();
        setModel(new LabelModel());
        getModel().addObserver(this);
        setDelegate(new HatenaTest(getModel()));
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setText("こんにちは");

        jButton1.setText("PUSH");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(103, 103, 103)
                        .addComponent(jLabel1))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(95, 95, 95)
                        .addComponent(jButton1)))
                .addContainerGap(108, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(59, 59, 59)
                .addComponent(jLabel1)
                .addGap(51, 51, 51)
                .addComponent(jButton1)
                .addContainerGap(59, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        getDelegate().run();
    }

    public void update(Observable o, Object arg) {
        jLabel1.setText(((LabelModel)o).getText());
    }

    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Hatena().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    private javax.swing.JLabel jLabel1;
    // End of variables declaration

}

class LabelModel extends Observable {

    private String text;

    public synchronized void setText(String newText) {
        if (!newText.equals(this.text)) {
            this.text = newText;
            setChanged();
            notifyObservers();
        }
    }

    public String getText() {
        return this.text;
    }

}

class HatenaTest {

    LabelModel model;

    private void setModel(LabelModel newModel) { this.model = newModel; }
    private LabelModel getModel() { return this.model; }

    public HatenaTest(LabelModel model) {
        setModel(model);
    }
    public void run() {
        model.setText("Hello");
    }
}