Listar dados do Banco de Dados no JComboBox

 boxPerfil = new JComboBox();
        boxPerfil.setBounds(110, 140, 100, 20);
        listarPerfil();

public void listarPerfil(){
        try{
            String perfil;
            boxPerfil.removeAllItems();
            objRs = objUsuario.perfil();
            if(objRs != null){
                while(objRs.next()){
                    perfil = objRs.getString("descricao");
                    boxPerfil.addItem(objRs.getString(perfil));
                }
            }
            else{
                JOptionPane.showMessageDialog(null, "objRs não possui nenhum item.");
            }
        }
        catch(SQLException e){
            JOptionPane.showMessageDialog(null, "ERRO");
            e.printStackTrace();
        }
    }

public ResultSet perfil(){
        try{
            
            objCon = con.conectar();
            String sqlPerfil = "SELECT * FROM crm_perfil";
            PreparedStatement objPerfil = objCon.prepareStatement(sqlPerfil);
            objRs = objPerfil.executeQuery();
            
            if(!objRs.next()){
                objRs = null;
            }
            else{
                objRs.first();
            }
        }
        
        catch(SQLException ex){
            JOptionPane.showMessageDialog(null, "ERRO SQL", "ERRO", JOptionPane.ERROR_MESSAGE);
            ex.printStackTrace();
        }
        
        return objRs;
    }

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at Usuario.CadastrarU.listarPerfil(CadastrarU.java:86)
	at Usuario.CadastrarU.<init>(CadastrarU.java:60)
	at MenuPrincipal.MenuPrincipal$3.actionPerformed(MenuPrincipal.java:148)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
	at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
	at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
	at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
	at java.awt.Component.processMouseEvent(Component.java:6535)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
	at java.awt.Component.processEvent(Component.java:6300)
	at java.awt.Container.processEvent(Container.java:2236)
	at java.awt.Component.dispatchEventImpl(Component.java:4891)
	at java.awt.Container.dispatchEventImpl(Container.java:2294)
	at java.awt.Component.dispatchEvent(Component.java:4713)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
	at java.awt.Container.dispatchEventImpl(Container.java:2280)
	at java.awt.Window.dispatchEventImpl(Window.java:2750)
	at java.awt.Component.dispatchEvent(Component.java:4713)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
	at java.awt.EventQueue$4.run(EventQueue.java:731)
	at java.awt.EventQueue$4.run(EventQueue.java:729)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)