Question

要更新问题，我已将产品和客户类附加到服务器和客户端类

之下如果我不清楚的话，我会提前在这里道歉。我正在尝试在String中显示ArrayList中包含的JTextField值。 String值会显示，但null值也会显示，我想显示String值。这是String

中显示的示例JTextField值

[nullDamonTholsonnull0, nullSylvesterStallonenull0, nullMisterTnull0]
[nullDamonTholsonnull0, nullSylvesterStallonenull0, nullMisterTnull0]
[nullDamonTholsonnull0, nullSylvesterStallonenull0, nullMisterTnull0]

在我的程序中，我有客户端用户界面从String Server请求Object值，然后在JTextField中显示它们。这是客户端界面代码：

private void jButtonDisplaycNamesActionPerformed(java.awt.event.ActionEvent evt) {
    {
        try {
            Socket socket = new Socket("localhost", 67);
            ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
            DataRequest request = new DataRequest(DataRequest.NAME);
            out.writeObject(request);
            out.flush();

            List<Customer> customerNames = (List<Customer>) in.readObject();
            jTextAreaOutput.setText("");

            for (Customer customerName : customerNames) {
                jTextAreaOutput.append(customerNames.toString());
                jTextAreaOutput.append("\n");
            }
            socket.close();
        } catch (Exception ex) {
            JOptionPane.showMessageDialog(this, "unable to contact Server");
            Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
        } // TODO add your handling code here:
    }

    // TODO add your handling code here:
}

private void jButtonDisplaycIDActionPerformed(java.awt.event.ActionEvent evt) {
    try {

        Socket socket = new Socket("localhost", 67);
        ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
        ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
        DataRequest request = new DataRequest(DataRequest.ID);
        out.writeObject(request);
        out.flush();
        List<Customer> customerIDs = (List<Customer>) in.readObject();
        jTextAreaOutput.setText("");
        for (Customer customerID : customerIDs) {
            jTextAreaOutput.append(customerIDs.toString());
            jTextAreaOutput.append("\n");
        }
        socket.close();
    } catch (Exception ex) {
        JOptionPane.showMessageDialog(this, "unable to contact Server");
        Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
    } // TODO add your handling code here:
}

private void jButtonDisplaypIDActionPerformed(java.awt.event.ActionEvent evt) {
    {
        try {

            Socket socket = new Socket("localhost", 67);
            ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
            DataRequest request = new DataRequest(DataRequest.PRODUCTID);
            out.writeObject(request);
            out.flush();

            List<Product> productIDs = (List<Product>) in.readObject();
            jTextAreaOutput.setText("");

            for (Product procuctID : productIDs) {
                jTextAreaOutput.append(productIDs.toString());
                jTextAreaOutput.append("\n");
            }
            socket.close();
        } catch (Exception ex) {
            JOptionPane.showMessageDialog(this, "unable to contact Server");
            Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
        } // TODO add your handling code here:
    }
}

这是服务器对象代码

public static void main(String[] args) throws IOException, ClassNotFoundException {

    ServerSocket server = new ServerSocket(67);
    while (true) {
        Socket socket = server.accept();
        ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
        ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());

        DataRequest request = (DataRequest) in.readObject();

        switch (request.getDataType()) {
            case DataRequest.NAME:
                out.writeObject(getCustomerName());
                out.flush();
                break;

            case DataRequest.ID:
                out.writeObject(getCustomerID());
                out.flush();
                break;

            case DataRequest.PASSWORD:
                out.writeObject(getCustomerPassword());
                out.flush();
                break;

            case DataRequest.DESCRIPTION:
                out.writeObject(getProductDescription());
                out.flush();
                break;
            case DataRequest.PRODUCTID:
                out.writeObject(getProductDescription());
                out.flush();
                break;

            case DataRequest.PRICE:
                out.writeObject(getProductDescription());
                out.flush();
                break;

        }
    }
}

private static List<Customer> getCustomerName() {
    List<Customer> names = new ArrayList<Customer>();
    in.readObject;
    Customer name = new Customer();
    name.setcFirstName("Damon");

    name.setcLastName("Tholson");

    names.add(name);

    name = new Customer();

    name.setcFirstName("Sylvester");
    name.setcLastName("Stallone");
    names.add(name);

    name = new Customer();

    name.setcFirstName("Mister");
    name.setcLastName("T");
    names.add(name);

    return names;
}

公共类Customer实现Serializable {

private String cID;
private String cFirstName;
private String cLastName;
private String cPassword;
private int dataType;




/**
 * @return the cID
 */
public String getcID() {
    return cID;
}

/**
 * @param cID the cID to set
 */
public void setcID(String cID) {
    this.cID = cID;
}

/**
 * @return the cFirstName
 */
public String getcFirstName() {
    return cFirstName;
}

/**
 * @param cFirstName the cFirstName to set
 */
public void setcFirstName(String cFirstName) {
    this.cFirstName = cFirstName;
}

/**
 * @return the cLastName
 */
public String getcLastName() {
    return cLastName;
}

/**
 * @param cLastName the cLastName to set
 */
public void setcLastName(String cLastName) {
    this.cLastName = cLastName;
}

/**
 * @return the cPassword
 */
public String getcPassword() {
    return cPassword;
}

/**
 * @param cPassword the cPassword to set
 */
public void setcPassword(String cPassword) {
    this.cPassword = cPassword;
}

/**
 * @return the dataType
 */
public int getDataType() {
    return dataType;
}

/**
 * @param dataType the dataType to set
 */
public void setDataType(int dataType) {
    this.dataType = dataType;
}

@Override
public String toString() {
    return  cID + cFirstName + cLastName +  cPassword +  dataType ;
}

public class Product实现Serializable {

private String pID;

private String pDescription;
private String pPrice;
private int dataType;



/**
 * @return the pID
 */
public String getpID() {
    return pID;
}

/**
 * @param pID the pID to set
 */
public void setpID(String pID) {
    this.pID = pID;
}

/**
 * @return the pName
 */
/**
 * @return the pDescription
 */
public String getpDescription() {
    return pDescription;
}

/**
 * @param pDescription the pDescription to set
 */
public void setpDescription(String pDescription) {
    this.pDescription = pDescription;
}

/**
 * @return the pPrice
 */
public String getpPrice() {
    return pPrice;
}

/**
 * @param pPrice the pPrice to set
 */
public void setpPrice(String pPrice) {
    this.pPrice = pPrice;
}

public int getDataType() {
    return dataType;
}

/**
 * @param dataType the dataType to set
 */
public void setDataType(int dataType) {
    this.dataType = dataType;
}

@Override
public String toString() {
    return pID + pDescription + pPrice;
}

/**
 * @return the dataType
 */

}

Answer 1

问题出在Client类中，它调用Customer类中toString方法的输出。我在toString方法中有多个返回但是我只调用了一个返回，所以我收到了我调用的变量和我没有调用的变量的空值。所以我的toString方法返回以下内容：

@覆盖 public String toString（） { return cFirstName + cID + cLastName + cPassword; }

但是我的Client类只调用该方法中的一个变量

for（Customer customerName：customerNames） { jTextAreaOutput.append（customerName.toString（））;

所以我改为调用特定变量

for（Customer customerName：customerNames） { jTextAreaOutput.append（customerName.getcFirstName（））;

尝试显示从Server对象检索的值时显示空值

1 个答案: