Erro ao implementar Singleton

public class Teste{

private Teste INSTANCIA = new Teste();
    private Teste(){
    }

    public static Teste show(){
    return INSTANCIA ;

   }

}

package exproperties;

import com.sun.swingset3.DemoProperties;
import javax.swing.JInternalFrame;

import org.jdesktop.application.Action;
import org.jdesktop.application.Application;
import org.jdesktop.application.ApplicationActionMap;
import org.jdesktop.swingx.JXTaskPane;

/**
 *
 * @author victor
 */
@DemoProperties(value = "Aplicativos",
category = "",
description = "Descrição da barra de menus",
sourceFiles = {
    "exproperties/ExPizza.java", "exproperties/resources/ExPizza.properties"
})
public class ExPizza extends javax.swing.JFrame {

    private JXTaskPane PrimeiroGroup;
    private JXTaskPane SegundoGroup;
    private JXTaskPane TerceiroGroup;

    public ExPizza() {
        initComponents();
        createTaskPane();
        bind();
        pack();
        Application.getInstance().getContext().getResourceMap(getClass()).injectComponents(this);
      }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jXTPContainerTeste = new org.jdesktop.swingx.JXTaskPaneContainer();
        desk = new javax.swing.JDesktopPane();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Formulario");

        jXTPContainerTeste.setName("jXTPContainerTeste"); // NOI18N

        desk.setEnabled(false);
        desk.setName("desk"); // NOI18N

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jXTPContainerTeste, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(desk, javax.swing.GroupLayout.PREFERRED_SIZE, 419, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(desk, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 244, Short.MAX_VALUE)
                    .addComponent(jXTPContainerTeste, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 244, Short.MAX_VALUE))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        
    private void createTaskPane() {
        PrimeiroGroup = new JXTaskPane();
        PrimeiroGroup.setName("PrimeiroGroupteste");
        jXTPContainerTeste.add(PrimeiroGroup);

        SegundoGroup = new JXTaskPane();
        SegundoGroup.setName("SegundoGroupteste");
        jXTPContainerTeste.add(SegundoGroup);

        TerceiroGroup = new JXTaskPane();
        TerceiroGroup.setName("TerceiroGroupteste");
        jXTPContainerTeste.add(TerceiroGroup);
    }

    private void bind() {
        ApplicationActionMap map = Application.getInstance().getContext().getActionMap(this);

        PrimeiroGroup.add(map.get("caracteristicas"));

        SegundoGroup.add(map.get("cliente"));

        TerceiroGroup.add(map.get("entrega"));
    }

    @Action
    public void caracteristicas()
    {
        internalPizza primeiroIFrame = (internalPizza) new JInternalFrame();

        desk.add(primeiroIFrame);
        primeiroIFrame.setVisible(true);
        primeiroIFrame.setBounds(10,10,400,200);
        primeiroIFrame.setClosable(true);
    }
   

    @Action
    public void cliente() 
    {
        internalDadosCliente segundoIFrame = new internalDadosCliente();

        desk.add(segundoIFrame);
        segundoIFrame.setVisible(true);
        segundoIFrame.setBounds(10,10,400,200);
        segundoIFrame.setClosable(true);
    }

    @Action
    public void entrega() 
    {
        internalDadosEntrega terceiroIFrame = new internalDadosEntrega();

        desk.add(terceiroIFrame);
        terceiroIFrame.setVisible(true);
        terceiroIFrame.setBounds(10,10,400,200);
        terceiroIFrame.setClosable(true);
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new ExPizza().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JDesktopPane desk;
    private org.jdesktop.swingx.JXTaskPaneContainer jXTPContainerTeste;
    // End of variables declaration                   
}

internalPizza primeiroIFrame = (internalPizza) new JInternalFrame();