Java 组合框错误

Question

我添加了一个组合框。它需要具有 1 到 20 的值，并且需要从构造函数调用方法。 现在我不擅长放置代码。我对需要在哪里插入代码感到困惑，并且总是会出现错误。

运行程序时出现错误。它对组合框说:没有合适的方法 我已将该框命名为yearscombobox

请帮我修复错误。我不知道是否需要放置具有 1 到 20 值的数组？如果是这样，我不知道该代码该放在哪里。 我在代码中用粗体编写的行中有错误。好吧，我尝试将其加粗。当我从 net beans 复制这段代码时，它几乎没有什么不同。任何有yearscomboox的东西都会出错，说没有合适的方法。帮我。我任由你摆布。我讨厌Java

  package murach.ui;

import java.text.NumberFormat;
 import murach.business.FinancialCalculations;

  public class FutureValueFrame extends javax.swing.JFrame {

   /** Creates new form FutureValueFrame */
    public FutureValueFrame() {
     initComponents();
    }

    /** This method is called from within the constructor to
    * initialize the form.
    * WARNING: Do NOT modify this code. The content of this method is
    * always regenerated by the Form Editor.
    */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
   private void initComponents() {

    jLabel1 = new javax.swing.JLabel();
    jLabel2 = new javax.swing.JLabel();
    jLabel3 = new javax.swing.JLabel();
    jLabel4 = new javax.swing.JLabel();
    monthlyPaymentTextField = new javax.swing.JTextField();
    yearlyRateTextField = new javax.swing.JTextField();
    calculateButton = new javax.swing.JButton();
    exitButton = new javax.swing.JButton();
    **YearsComboBox = new javax.swing.JComboBox();**
    jScrollPane1 = new javax.swing.JScrollPane();
    FutureValueList = new javax.swing.JList();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setTitle("Future Value Calculator");
    setResizable(false);

    jLabel1.setText("Monthly Payment:");

    jLabel2.setText("Yearly Interest Rate:");

    jLabel3.setText("Number of Years:");

    jLabel4.setText("Future Value:");

    calculateButton.setMnemonic('c');
    calculateButton.setText("Calculate");
    calculateButton.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            calculateButtonActionPerformed(evt);
        }
    });

    exitButton.setMnemonic('x');
    exitButton.setText("Exit");
    exitButton.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            exitButtonActionPerformed(evt);
        }
    });

    YearsComboBox.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20" }));
    YearsComboBox.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            YearsComboBoxActionPerformed(evt);
        }
    });

    FutureValueList.setModel(new javax.swing.AbstractListModel() {
        String[] strings = { "Year 1", "Year 2", "Year 3", "Year 4", "Year 5" };
        public int getSize() { return strings.length; }
        public Object getElementAt(int i) { return strings[i]; }
    });
    jScrollPane1.setViewportView(FutureValueList);

    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()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jLabel1)
                .addComponent(jLabel2)
                .addComponent(jLabel3)
                .addComponent(jLabel4))
            .addGap(16, 16, 16)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addComponent(yearlyRateTextField)
                    .addComponent(monthlyPaymentTextField, javax.swing.GroupLayout.DEFAULT_SIZE, 115, Short.MAX_VALUE)
                    .addComponent(YearsComboBox, javax.swing.GroupLayout.PREFERRED_SIZE, 67, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(layout.createSequentialGroup()
                    .addGap(6, 6, 6)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addGroup(layout.createSequentialGroup()
                            .addComponent(calculateButton, javax.swing.GroupLayout.PREFERRED_SIZE, 90, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 26, Short.MAX_VALUE)
                            .addComponent(exitButton, javax.swing.GroupLayout.PREFERRED_SIZE, 65, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addComponent(jScrollPane1))))
            .addGap(36, 36, 36))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel1)
                .addComponent(monthlyPaymentTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel2)
                .addComponent(yearlyRateTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel3)
                .addComponent(YearsComboBox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jLabel4)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 56, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(18, 18, 18)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(calculateButton)
                .addComponent(exitButton))
            .addContainerGap(100, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>


private void calculateButtonActionPerformed(java.awt.event.ActionEvent evt) {                                                
    if (isValidData())
    {
        double p = Double.parseDouble(monthlyPaymentTextField.getText());
        double r = Double.parseDouble(yearlyRateTextField.getText());
        int y = Integer.parseInt(YearsComboBox.getItemCount());

        double fv = FinancialCalculations.calculateFutureValue(p, r, y);

        NumberFormat currency = NumberFormat.getCurrencyInstance();
        FutureValueList.setText(currency.format(fv));
    }
}                                               

private void exitButtonActionPerformed(java.awt.event.ActionEvent evt) {                                           
    System.exit(0);
}                                          

private void YearsComboBoxActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:
 int y = YearsComboBox.getSelectedIndex();

}

private boolean isValidData()
{
    SwingValidator sv = new SwingValidator();
    return
        sv.isPresent(monthlyPaymentTextField, "Monthly Investment") &&
        sv.isDouble(monthlyPaymentTextField, "Monthly Investment") &&
        sv.isPresent(yearlyRateTextField, "Interest Rate") &&
        sv.isDouble(yearlyRateTextField, "Interest Rate") &&
        sv.isPresent(YearsComboBox, "Number of Years") &&
        sv.isInteger(YearsComboBox, "Number of Years");
}

/**
* @param args the command line arguments
*/
public static void main(String args[]) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            // new FutureValueFrame().setVisible(true);  // generated code
            FutureValueFrame frame = new FutureValueFrame();
            frame.setVisible(true);
            frame.setLocationRelativeTo(null);
        }
    });
}

// Variables declaration - do not modify
private javax.swing.JList FutureValueList;
public javax.swing.JComboBox YearsComboBox;
private javax.swing.JButton calculateButton;
private javax.swing.JButton exitButton;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextField monthlyPaymentTextField;
private javax.swing.JTextField yearlyRateTextField;
// End of variables declaration

  }

Answer 1

1. 为了获得更好的帮助，请尽快发布 SSCCE ，没人知道剩下的类(class)...，

2. 将 Integer 或 Double 值放入 JComboBox 的 Model 没有问题或JList

3. 使用 J FormattedTextField使用数字格式化程序，

4. 那么您可以减少从/解析 String 到 Integer 或 Double 时可能出现的异常

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5. 您可以使用JSpinner with SpinnerDateModel而不是 JComboBox