Jpanel Ajuda

OLA PESSOAL
fiz uma panel no netbeans e nao estou consegundo adicionalo noJframe se alguem puder me ajudar fico muito grato segue a baixo codigodo panel e do jframe.

/*
 * Explorer_panel.java
 *
 * Created on 10 de Julho de 2007, 21:04
 */

package GUI;


/**
 *
 * @author  Cleyton
 */
public class Explorer_panel extends javax.swing.JPanel{
    
    /** Creates new form Explorer_panel */
    public Explorer_panel() {
        initComponents();
    }
    
    /** 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=" Código Gerado ">                          
    private void initComponents() {
        jScrollPane1 = new javax.swing.JScrollPane();
        jTree1 = new javax.swing.JTree();
        jComboBox1 = new javax.swing.JComboBox();
        jScrollPane2 = new javax.swing.JScrollPane();
        jSlider1 = new javax.swing.JSlider();
        jButton1 = new javax.swing.JButton();
        jTextField1 = new javax.swing.JTextField();
        jLabel1 = new javax.swing.JLabel();

        jScrollPane1.setViewportView(jTree1);

        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

        jScrollPane2.setBackground(java.awt.Color.white);

        jSlider1.setBackground(java.awt.Color.white);

        jButton1.setBackground(java.awt.Color.white);
        jButton1.setText("Adicionar");

        jLabel1.setBackground(java.awt.Color.white);
        jLabel1.setText("Amplia");

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(jComboBox1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 528, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                    .add(layout.createSequentialGroup()
                        .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                            .add(org.jdesktop.layout.GroupLayout.TRAILING, layout.createSequentialGroup()
                                .add(jTextField1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 184, Short.MAX_VALUE)
                                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                                .add(jButton1)
                                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED))
                            .add(org.jdesktop.layout.GroupLayout.TRAILING, jScrollPane1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 267, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                        .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                        .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                            .add(jSlider1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 255, Short.MAX_VALUE)
                            .add(jScrollPane2, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 255, Short.MAX_VALUE)
                            .add(layout.createSequentialGroup()
                                .add(10, 10, 10)
                                .add(jLabel1)))))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .add(17, 17, 17)
                .add(jComboBox1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING, false)
                    .add(jScrollPane2)
                    .add(jScrollPane1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 295, Short.MAX_VALUE))
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                .add(jLabel1)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.TRAILING)
                    .add(jSlider1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                    .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                        .add(jTextField1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                        .add(jButton1)))
                .addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
    }// </editor-fold>                        
    
    
    // Declaração de variáveis - não modifique                     
    private javax.swing.JButton jButton1;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JSlider jSlider1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTree jTree1;
    // Fim da declaração de variáveis                   
    
}

JFrame que nao esta dando certo

/*
 * Aplicacao_gui.java
 *
 * Created on 10 de Julho de 2007, 21:05
 */

package GUI;

/**
 *
 * @author  Cleyton
 */
public class Aplicacao_gui extends javax.swing.JFrame {
    
    /** Creates new form Aplicacao_gui */
    public Aplicacao_gui() {
        initComponents();
    }
//=============================================================================    
 Explorer_panel explorer;
 //metodo criado para instanciar penals
 public void instancias(){
     explorer = new Explorer_panel();
     //setLayeredPane(DEFAULT_LAYER);
     //getContentPane().setLayout();
     //getContentPane().add(explorer);
     
     
 }   
//=============================================================================    
    /** 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=" Código Gerado ">                          
    private void initComponents() {
        jPanel1 =  new Explorer_panel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        org.jdesktop.layout.GroupLayout jPanel1Layout = new org.jdesktop.layout.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 407, Short.MAX_VALUE)
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 339, Short.MAX_VALUE)
        );

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(174, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(178, Short.MAX_VALUE))
        );
        pack();
    }// </editor-fold>                        
    
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Aplicacao_gui().setVisible(true);
            }
        });
    }
    
    // Declaração de variáveis - não modifique                     
    private javax.swing.JPanel jPanel1;
    // Fim da declaração de variáveis                   
    
}

O main do aplicativo

/*
 * Main.java
 *
 * Created on 10 de Julho de 2007, 21:00
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package pdi_aplicate;
import GUI.Aplicacao_gui;

/**
 *
 * @author Cleyton
 */
public class Main {
    
    /** Creates a new instance of Main */
    public Main() {
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Aplicacao_gui().setVisible(true);
            }
        });
    }
    
}