How to Get the value of a multiplication?

Question

System made in Vaadin + Java + Springboot + Maven + Mysql

I have a sales system, where the user chooses the product he wants to buy in a Combobox, sets the amount he wants to buy (Numberfield), when selecting the product the field Unit Value(Textfield) is filled automatically with the value saved in MYSQL.

Problem: How do I, when the user sets the amount(Numberfield) automatically multiply Unit Value(Textfield) and the value of this multiplication appears in the Total Item Value field(Numberfield)?

See in the image below I bought 2 motherboards, but the total item value is 0

How to Get the Right Result?

I tried with this code:

txtQuantidade.setHasControls(true);
txtQuantidade.setValue(null);
txtQuantidade.setMin(1);
        
txtQuantidade.addValueChangeListener(event -> {        
    String valorUnitario = txtValorUnitario.getValue().replace(".", ",");
    Number number = 0;
    try {
        number = NumberFormat.getInstance().parse(valorUnitario);
    } catch (ParseException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
    
    float valorUnitarioFloat = Float.parseFloat(String.valueOf(number));

    txtValorTotalItem.setValue(valorUnitarioFloat * txtQuantidade.getValue());
});

but with this code I only got this error:

java.text.ParseException: Unparseable number: "R$ 549,90"
  at java.base/java.text.NumberFormat.parse(NumberFormat.java:434)
  at br.com.fjsistemas.cadastros.view.VendaView.lambda$13(VendaView.java:265)
  at com.vaadin.flow.component.internal.AbstractFieldSupport.lambda$addValueChangeListener$828eca10$1(AbstractFieldSupport.java:96)
  at com.vaadin.flow.component.ComponentEventBus.fireEventForListener(ComponentEventBus.java:205)
  at com.vaadin.flow.component.ComponentEventBus.fireEvent(ComponentEventBus.java:194)
  at com.vaadin.flow.component.Component.fireEvent(Component.java:359)
  at com.vaadin.flow.component.ComponentUtil.fireEvent(ComponentUtil.java:386)
  at com.vaadin.flow.component.internal.AbstractFieldSupport.setValue(AbstractFieldSupport.java:207)
  at com.vaadin.flow.component.internal.AbstractFieldSupport.setModelValue(AbstractFieldSupport.java:167)
  at com.vaadin.flow.component.AbstractField.setModelValue(AbstractField.java:225)
  at com.vaadin.flow.component.AbstractSinglePropertyField.handlePropertyChange(AbstractSinglePropertyField.java:352)
  at com.vaadin.flow.component.AbstractSinglePropertyField.access$200(AbstractSinglePropertyField.java:48)
  at com.vaadin.flow.component.AbstractSinglePropertyField$1.propertyChange(AbstractSinglePropertyField.java:325)
  at com.vaadin.flow.internal.nodefeature.ElementPropertyMap.lambda$fireEvent$2(ElementPropertyMap.java:454)
  at java.base/java.util.ArrayList.forEach(ArrayList.java:1507)
  at com.vaadin.flow.internal.nodefeature.ElementPropertyMap.fireEvent(ElementPropertyMap.java:454)
  at com.vaadin.flow.internal.nodefeature.ElementPropertyMap.access$100(ElementPropertyMap.java:48)
  at com.vaadin.flow.internal.nodefeature.ElementPropertyMap$PutResult.run(ElementPropertyMap.java:166)
  at com.vaadin.flow.server.communication.ServerRpcHandler.runMapSyncTask(ServerRpcHandler.java:395)
  at com.vaadin.flow.server.communication.ServerRpcHandler.lambda$handleInvocations$0(ServerRpcHandler.java:389)
  at java.base/java.util.ArrayList.forEach(ArrayList.java:1507)
  at com.vaadin.flow.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:389)
  at com.vaadin.flow.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:317)
  at com.vaadin.flow.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:89)
  at com.vaadin.flow.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:40)
  at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1547)
  at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:247)
  at com.vaadin.flow.spring.SpringServlet.service(SpringServlet.java:111)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
  at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
  at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:459)
  at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:352)
  at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
  at org.springframework.web.servlet.mvc.ServletForwardingController.handleRequestInternal(ServletForwardingController.java:141)
  at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:177)
  at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:52)
  at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060)
  at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962)
  at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
  at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
  at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
  at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
  at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
  at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
  at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
  at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
  at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
  at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
  at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
  at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
  at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
  at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:888)
  at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1597)
  at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
  at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
  at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
  at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
  at java.base/java.lang.Thread.run(Thread.java:830)

Answer 1

resolved as follows:

package br.com.fjsistemas.cadastros.view;

import java.text.NumberFormat;
import java.text.ParseException;
import java.time.LocalDate;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

import javax.annotation.PostConstruct;

import org.springframework.beans.factory.annotation.Autowired;
import org.vaadin.textfieldformatter.CustomStringBlockFormatter;

import com.vaadin.flow.component.Component;
import com.vaadin.flow.component.button.Button;
import com.vaadin.flow.component.button.ButtonVariant;
import com.vaadin.flow.component.combobox.ComboBox;
import com.vaadin.flow.component.datepicker.DatePicker;
import com.vaadin.flow.component.dialog.Dialog;
import com.vaadin.flow.component.formlayout.FormLayout;
import com.vaadin.flow.component.grid.Grid;
import com.vaadin.flow.component.grid.GridVariant;
import com.vaadin.flow.component.html.Div;
import com.vaadin.flow.component.html.Label;
import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.component.tabs.Tab;
import com.vaadin.flow.component.tabs.Tabs;
import com.vaadin.flow.component.textfield.NumberField;
import com.vaadin.flow.component.textfield.TextField;
import com.vaadin.flow.data.binder.Binder;
import com.vaadin.flow.data.binder.PropertyId;
import com.vaadin.flow.data.renderer.NumberRenderer;
import com.vaadin.flow.router.PageTitle;
import com.vaadin.flow.router.Route;

import br.com.fjsistemas.backend.Cliente;
import br.com.fjsistemas.backend.Produto;
import br.com.fjsistemas.backend.Venda;
import br.com.fjsistemas.main.MainView;
import br.com.fjsistemas.repository.ClienteRepository;
import br.com.fjsistemas.repository.ProdutoRepository;
import br.com.fjsistemas.service.VendaService;

@Route(value = "venda-view", layout = MainView.class)
@PageTitle("Lançamento de Vendas")
public class VendaView extends VerticalLayout {

    private static final long serialVersionUID = 1L;

    private HorizontalLayout hltVenda = new HorizontalLayout();
    Grid<Venda> grdVenda = new Grid<>(Venda.class, false);

    private HorizontalLayout hltBarraBotoes = new HorizontalLayout();
    Button btnNovo = new Button("Novo");
    Button btnAlterar = new Button("Alterar");
    Button btnExcluir = new Button("Excluir");

    private Dialog dlgJanela = new Dialog();

    private FormLayout fltCamposVenda = new FormLayout();

    HorizontalLayout primeiraLinhaGuiaVenda = new HorizontalLayout();
    HorizontalLayout segundaLinhaGuiaVenda = new HorizontalLayout();
    HorizontalLayout terceiraLinhaGuiaVenda = new HorizontalLayout();
    HorizontalLayout quartaLinhaGuiaVenda = new HorizontalLayout();

    @PropertyId("data")
    private DatePicker txtDataVenda = new DatePicker("Data Venda");

    @PropertyId("nome")
    private ComboBox<Cliente> txtNomeCliente = new ComboBox<>();

    @PropertyId("telefone")
    private TextField txtTelefone = new TextField("Telefone");

    @PropertyId("celular")
    private TextField txtCelular = new TextField("Celular");

    @PropertyId("produtos")
    private ComboBox<Produto> txtProdutos = new ComboBox<>();

    @PropertyId("quantidade")
    private NumberField txtQuantidade = new NumberField("Quantidade");

    @PropertyId("unitario")
    private TextField txtValorUnitario = new TextField("Valor Unitário");

    @PropertyId("valorTotalItem")
    private TextField txtValorTotalItem = new TextField("Valor Total Item");

    @PropertyId("campoSomaValores")
    private NumberField campoSomaValores = new NumberField();

    private HorizontalLayout htlDlgBarraBotoes = new HorizontalLayout();
    private Button btnSalvar = new Button("Salvar");
    private Button btnFechar = new Button("Fechar");
    private Button btnAdicionarItem = new Button("Adicionar Item");

    @Autowired
    VendaService vendaService;

    @Autowired
    ClienteRepository clienteRepository;

    @Autowired
    ProdutoRepository produtoRepository;

    private List<Venda> listaVendas;
    private Venda venda;

    Binder<Venda> binderVenda = new Binder<>(Venda.class);

    public VendaView() {

    }

    @PostConstruct
    public void init() {
        configuraTela();

    }

    private void configuraTela() {

        setMargin(false);
        setPadding(false);

        configuraHltVenda();
        configuraFltBarraBotoes();
        configuraDlgJanela();
        populaGrdVenda();
        configuraBinder();

        add(hltVenda, hltBarraBotoes);
    }

    private void configuraFltBarraBotoes() {

        btnNovo.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        btnNovo.addClickListener(e -> {
            novoClick();
        });

        btnAlterar.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        btnAlterar.addClickListener(e -> {
            alterarClick();
        });

        btnExcluir.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        btnExcluir.addClickListener(e -> {
            excluirClick();
        });

        hltBarraBotoes.add(btnNovo, btnAlterar, btnExcluir);
    }

    private void excluirClick() {

        if (venda != null) {
            listaVendas.remove(venda);
            vendaService.delete(venda);
            atualizaGrdVenda();
        }
    }

    private void configuraHltVenda() {
        hltVenda.setWidthFull();
        configuraGrdVenda();
        hltVenda.add(grdVenda);
    }

    private void configuraGrdVenda() {
        grdVenda.setHeight("820px");
        grdVenda.setWidthFull();

        grdVenda.addColumn(Venda::getId).setHeader("ID:").setAutoWidth(true);

        grdVenda.addColumn(Venda::getDataVenda).setHeader("Data Venda:").setAutoWidth(true).setKey("dataVenda");

        grdVenda.addColumn(Venda::getNomeCliente).setHeader("Nome:").setAutoWidth(true).setKey("nome");

        grdVenda.addColumn(new NumberRenderer<>(Venda::getValorTotalVenda, "R$ %(,.2f", Locale.getDefault(), "R$ 0.00"))
                .setHeader("Valor Total:").setAutoWidth(true).setKey("valorTotalVenda");

        grdVenda.addThemeVariants(GridVariant.LUMO_COMPACT, GridVariant.LUMO_COLUMN_BORDERS);

        grdVenda.getColumns().forEach(col -> col.setAutoWidth(true).setSortable(true).setResizable(true));

        grdVenda.addItemClickListener(e -> {
            venda = e.getItem();
        });

    }

    private void configuraDlgJanela() {

        dlgJanela.setHeight("755px");
        dlgJanela.setWidth("860px");

        Tab vender = new Tab("Vendas");
        Div venderDiv = new Div();

        Tab entrega = new Tab("Entregas");
        Div entregaDiv = new Div();
        entregaDiv.setVisible(false);

        Tab financeiro = new Tab("Financeiro");
        Div financeiroDiv = new Div();
        financeiroDiv.setVisible(false);

//=====================================================================================================================

        txtNomeCliente.setWidth("390px");
        txtNomeCliente.setLabel("Nome Cliente");

        List<Cliente> listaDeClientes = clienteRepository.findAll();
        txtNomeCliente.setItemLabelGenerator(Cliente::getNome);
        txtNomeCliente.setItems(listaDeClientes);
        txtNomeCliente.addValueChangeListener(event -> {
            txtTelefone.setValue(event.getValue().getFone());
            txtCelular.setValue(event.getValue().getCelular());
        });

        new CustomStringBlockFormatter.Builder().blocks(0, 2, 4, 4).delimiters("(", ")", "-").numeric().build()
                .extend(txtTelefone);

        new CustomStringBlockFormatter.Builder().blocks(0, 2, 5, 4).delimiters("(", ")", "-").numeric().build()
                .extend(txtCelular);

//=====================================================================================================================

        txtProdutos.setWidth("370px");
        txtProdutos.setLabel("Produtos");
        List<Produto> listaDeProdutos = produtoRepository.findAll();
        txtProdutos.setItemLabelGenerator(Produto::getNome);
        txtProdutos.setItems(listaDeProdutos);
        txtProdutos.addValueChangeListener(event -> {

            NumberFormat formatter = NumberFormat.getCurrencyInstance(new Locale("pt", "BR"));
            try {

                txtValorUnitario.setValue(formatter.format(event.getValue().getValor()));

            } catch (Exception e) {
                e.printStackTrace();
            }

        });

//==========================================================================================================================

        txtQuantidade.setHasControls(true);
        txtQuantidade.setValue(null);
        txtQuantidade.setMin(1);

        txtQuantidade.addValueChangeListener(event -> {
              
            NumberFormat formatter = NumberFormat.getCurrencyInstance(new Locale("pt", "BR"));
            double valorTotal = 0;
            try {
                valorTotal = formatter.parse(txtValorUnitario.getValue()).doubleValue() * txtQuantidade.getValue();
            } catch (ParseException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            } txtValorTotalItem.setValue(formatter.format(valorTotal));
        });

//==========================================================================================================================

        Label text = new Label("Valor Total da Compra");
        text.getElement().getStyle().set("fontWeight", "bold");
        text.getStyle().set("margin-top", "25em");
        text.getStyle().set("margin-left", "24em");
        text.getStyle().set("text-align", "center");
        campoSomaValores.getStyle().set("margin-top", "25em");
        campoSomaValores.setWidth("30em");

        segundaLinhaGuiaVenda.add(txtNomeCliente, txtTelefone, txtCelular);
        terceiraLinhaGuiaVenda.add(txtProdutos, txtQuantidade, txtValorUnitario, txtValorTotalItem);
        quartaLinhaGuiaVenda.add(text, campoSomaValores);

        fltCamposVenda.add(venderDiv, entregaDiv, financeiroDiv);
        venderDiv.add(txtDataVenda, segundaLinhaGuiaVenda, terceiraLinhaGuiaVenda, quartaLinhaGuiaVenda);
        vender.add(venderDiv);

        LocalDate now = LocalDate.now();
        txtDataVenda.setValue(now);

        Map<Tab, Component> tabsToPages = new HashMap<>();
        tabsToPages.put(vender, venderDiv);
        tabsToPages.put(entrega, entregaDiv);
        tabsToPages.put(financeiro, financeiroDiv);
        Tabs tabs = new Tabs(vender, entrega, financeiro);
        Div pages = new Div(venderDiv, entregaDiv, financeiroDiv);

        tabs.addSelectedChangeListener(event -> {
            tabsToPages.values().forEach(page -> page.setVisible(false));
            Component selectedPage = tabsToPages.get(tabs.getSelectedTab());
            selectedPage.setVisible(true);
        });

        dlgJanela.add(tabs, pages);

        btnSalvar.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        btnSalvar.getStyle().set("margin-top", "-3em");
        btnSalvar.getStyle().set("margin-left", "0em");
        btnSalvar.addClickListener(e -> {
            salvarClick();
        });

        btnFechar.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        btnFechar.getStyle().set("margin-top", "-3em");
        btnFechar.addClickListener(e -> {
            dlgJanela.close();
        });

        btnAdicionarItem.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        btnAdicionarItem.getStyle().set("margin-top", "-3em");
        btnAdicionarItem.addClickListener(e -> {

        });

        htlDlgBarraBotoes.add(btnSalvar, btnFechar, btnAdicionarItem);

        dlgJanela.add(fltCamposVenda, htlDlgBarraBotoes);
    }

    private void salvarClick() {

        venda = binderVenda.getBean();

        boolean adicionarLista = venda.getId() == null ? true : false;

        vendaService.create(venda);

        if (adicionarLista) {
            listaVendas.add(venda);
        }
        atualizaGrdVenda();
        novaVenda();
        txtNomeCliente.focus();

        binderVenda.setBean(venda);

        if (adicionarLista) {
            dlgJanela.close();
        }
    }

    private void populaGrdVenda() {

        listaVendas = vendaService.read();
        atualizaGrdVenda();
    }

    private void atualizaGrdVenda() {
        grdVenda.setItems(listaVendas);
    }

    private void configuraBinder() {

        binderVenda.bindInstanceFields(this);

    }

    private void novoClick() {

        novaVenda();
        binderVenda.setBean(venda);

        dlgJanela.open();
        txtNomeCliente.focus();
    }

    private void alterarClick() {

        if (venda != null) {
            binderVenda.setBean(venda);

            dlgJanela.open();

        }
    }

    private void novaVenda() {
        venda = new Venda();
        venda.setNomeCliente(" ");
        dlgJanela.close();

    }
}

Answer 2

The value you have is "R$ 549,90" it is not possible to convert this String to a numerical value, first you must leave only the numbers inside the String. Obs leave the string with the . to convert its value.

When you have your double value you will be able to do your calculation.

String txtValorUnitario = "R$ 549.90";
String valorUnitario2 = txtValorUnitario.replace("R$ ", "");
double meuValorNumerico = Double.parseDouble(valorUnitario2);