estou tentando criar um PostBack no meu projeto, mais sempre que eu submeto o formulário ele traz select que possuo no meu formulário. Ou seja, fica a mesma coisa padrão

public class FacesUtil {

    /**
     * Método que avalia se é postBack.
     * @return
     */
    public boolean isPostback(){
        return FacesContext.getCurrentInstance().isPostback();
    }

    /**
     * Método que nega o PostBack
     * @return
     */
    public static boolean isNotPostBack(){
        return !isNotPostBack();
    }

}

meu Bean

package com.irmaosuspension.controleservico.controller;

import java.io.Serializable;
import java.util.Arrays;
import java.util.List;

import javax.faces.view.ViewScoped;
import javax.inject.Inject;
import javax.inject.Named;

import org.omnifaces.util.Messages;

import com.irmaosuspension.controleservico.enumeration.Categoria;
import com.irmaosuspension.controleservico.jsf.FacesUtil;
import com.irmaosuspension.controleservico.modelo.Fabricante;
import com.irmaosuspension.controleservico.modelo.ModeloCarro;
import com.irmaosuspension.controleservico.service.FabricanteService;
import com.irmaosuspension.controleservico.service.ModeloCarroService;
import com.irmaosuspension.controleservico.util.NegocioException;

import lombok.Getter;
import lombok.Setter;


@Named
@ViewScoped
public class CadastroModeloCarroBean implements Serializable {

    private static final long serialVersionUID = 1L;

    @Inject
    private FabricanteService fabricanteService;

    @Inject
    private ModeloCarroService modeloCarroService;

    @Getter
    private List<Fabricante> fabricantes;
    @Getter
    private List<Categoria> categorias;

    @Getter
    @Setter
    private Fabricante fabricante;
    @Getter
    @Setter
    private ModeloCarro modeloCarro;

    public void inicializar() {
        System.out.println("Iniciando Modelo Carro");

        if(FacesUtil.isNotPostBack()){
            fabricantes = fabricanteService.buscarTodos();
            categorias = Arrays.asList(Categoria.values());
        }

        if (this.modeloCarro == null) {
            limpar();
        }

    }

    public void salvar() throws NegocioException {
        try {
            modeloCarroService.salvar(modeloCarro);
            Messages.addGlobalInfo("Carro salvo com sucesso!");
            limpar();
        } catch (NegocioException e) {
            Messages.addGlobalError(e.getMessage());
        }
    }

    public void excluir(){
        try {
            modeloCarroService.excluir(modeloCarro);
            Messages.addGlobalInfo("Carro excluído com sucesso!");
        } catch (NegocioException e) {
            Messages.addGlobalError(e.getMessage());
        }
    }


    public boolean isEditando() {
        return this.modeloCarro.getCodigo() != null;
    }

    private void limpar() {
        this.modeloCarro = new ModeloCarro();
    }

}

Erro

GRAVE: Servlet.service() for servlet [Faces Servlet] in context with path [/suspension] threw exception [Unresolved compilation problem: 
    The method isNotPostBack() is undefined for the type FacesUtil
] with root cause
java.lang.Error: Unresolved compilation problem: 
    The method isNotPostBack() is undefined for the type FacesUtil

    at com.irmaosuspension.controleservico.controller.CadastroModeloCarroBean.inicializar(CadastroModeloCarroBean.java:52)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:247)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:267)
    at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
    at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at com.sun.faces.facelets.tag.jsf.core.DeclarativeSystemEventListener.processEvent(EventHandler.java:128)
    at javax.faces.component.UIComponent$ComponentSystemEventListenerAdapter.processEvent(UIComponent.java:2584)
    at javax.faces.event.SystemEvent.processListener(SystemEvent.java:108)
    at javax.faces.event.ComponentSystemEvent.processListener(ComponentSystemEvent.java:118)
    at com.sun.faces.application.ApplicationImpl.processListeners(ApplicationImpl.java:2169)
    at com.sun.faces.application.ApplicationImpl.invokeComponentListenersFor(ApplicationImpl.java:2114)
    at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:287)
    at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:245)
    at javax.faces.application.ApplicationWrapper.publishEvent(ApplicationWrapper.java:726)
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:107)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:659)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:495)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:767)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1347)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)