Problema ao executar .jar

public class main {
    
    /**
     * Creates a new instance of main
     */
    public main() {
       
    }
    public static void main(String [] args) {
        Menu menu = new Menu();
        menu.setVisible(true);
    }
    
}

public class Menu extends javax.swing.JFrame {
    CadastroFornec cadf = new CadastroFornec();
    Cadastro cad = new Cadastro();
   
    
    /** Creates new form Menu */
    public Menu() {
        initComponents();
        
    }
    
                

    private void jMenuItem1ActionPerformed(java.awt.event.ActionEvent evt) {                                           

        cad.setVisible(true);
        this.dispose();
    }                                          

    private void jMenuItem3ActionPerformed(java.awt.event.ActionEvent evt) {                                           
         Vendas1 vd = new Vendas1();
          vd.setVisible(true);
        this.dispose();
    }                                          
 //ir para cadFornec
    private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        cadf.setVisible(true);
        this.dispose();
    }                                          


//ir para cadClientes
    private void jMenuItem2ItemStateChanged(java.awt.event.ItemEvent evt) {                                            

        
    }                                           
    
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Menu().setVisible(true);
            }
        });
    }
    
    // Variables declaration - do not modify                     
    private javax.swing.JMenu jMenu1;
    private javax.swing.JMenu jMenu2;
    private javax.swing.JMenuBar jMenuBar1;
    private javax.swing.JMenuItem jMenuItem1;
    private javax.swing.JMenuItem jMenuItem2;
    private javax.swing.JMenuItem jMenuItem3;
    // End of variables declaration                   
    
}