Java 未找到数据时如何使用showMessageDialog

我正在制作一个小程序，它与数据库连接。现在我正在做一个搜索选项，你需要把你的搜索条件放在一个文本框中，然后点击“搜索”按钮。我成功地做到了这一点，只是现在我需要扩展它。 当您点击“搜索”按钮后未找到数据时，需要弹出一个ShowMessage对话框，其中显示“未找到与您的搜索条件匹配的数据”

String naam = zoekField.getText();

try {
    DefaultComboBoxModel dier = new DefaultComboBoxModel();

    Connection conn = SimpleDataSourceV2.getConnection();

    Statement stat = conn.createStatement();

    ResultSet rs = stat.executeQuery("SELECT * FROM dier WHERE rnaam = '" + naam + "';");

    ModelItem item;

    if(rs.next()) {
        do{
           item = new ModelItem();
           item.roepnaam = rs.getString("rnaam");
           item.geslacht = rs.getString("gesl");
           item.snr = rs.getInt("snr");
           dier.addElement(item);
        }while(rs.next());
    }else{
        JOptionPane.showMessageDialog(this, "No data found");
    }
    rs.close();

    stat.close();

    lijst.setModel(dier);

} catch (SQLException e) {
    JOptionPane.showMessageDialog(this, e.getMessage());
}

我怎样才能做到这一点？如何将其集成到现有代码中

String naam = zoekField.getText();

try {
    DefaultComboBoxModel dier = new DefaultComboBoxModel();

    Connection conn = SimpleDataSourceV2.getConnection();

    Statement stat = conn.createStatement();

    ResultSet rs = stat.executeQuery("SELECT * FROM dier WHERE rnaam = '" + naam + "';");

    ModelItem item;

    if(rs.next()) {
        do{
           item = new ModelItem();
           item.roepnaam = rs.getString("rnaam");
           item.geslacht = rs.getString("gesl");
           item.snr = rs.getInt("snr");
           dier.addElement(item);
        }while(rs.next());
    }else{
        JOptionPane.showMessageDialog(this, "No data found");
    }
    rs.close();

    stat.close();

    lijst.setModel(dier);

} catch (SQLException e) {
    JOptionPane.showMessageDialog(this, e.getMessage());
}

这是我目前的搜索方法：

private void zoekButtonActionPerformed(java.awt.event.ActionEvent evt) {                                           

    String naam = zoekField.getText();

    try {
        DefaultComboBoxModel dier = new DefaultComboBoxModel();

        Connection conn = SimpleDataSourceV2.getConnection();

        Statement stat = conn.createStatement();

        ResultSet rs = stat.executeQuery("SELECT * FROM dier WHERE rnaam = '" + naam + "';");

        ModelItem item;

        while (rs.next()) {
            item = new ModelItem();
            item.roepnaam = rs.getString("rnaam");
            item.geslacht = rs.getString("gesl");
            item.snr = rs.getInt("snr");
            dier.addElement(item);
        }
        rs.close();

        stat.close();

        lijst.setModel(dier);

    } catch (SQLException e) {
        JOptionPane.showMessageDialog(this, e.getMessage());
    }

String naam = zoekField.getText();

try {
    DefaultComboBoxModel dier = new DefaultComboBoxModel();

    Connection conn = SimpleDataSourceV2.getConnection();

    Statement stat = conn.createStatement();

    ResultSet rs = stat.executeQuery("SELECT * FROM dier WHERE rnaam = '" + naam + "';");

    ModelItem item;

    if(rs.next()) {
        do{
           item = new ModelItem();
           item.roepnaam = rs.getString("rnaam");
           item.geslacht = rs.getString("gesl");
           item.snr = rs.getInt("snr");
           dier.addElement(item);
        }while(rs.next());
    }else{
        JOptionPane.showMessageDialog(this, "No data found");
    }
    rs.close();

    stat.close();

    lijst.setModel(dier);

} catch (SQLException e) {
    JOptionPane.showMessageDialog(this, e.getMessage());
}

---

}

我认为在while外观之前检查rs.isLast（）或rs.isAfterLast（）应该会有所帮助。我不能100%确定哪个是正确的，但我认为应该是rs.isAfterLast（）。

private void zoekbuttonationperformed（java.awt.event.ActionEvent evt）{

String naam = zoekField.getText();

try {
    DefaultComboBoxModel dier = new DefaultComboBoxModel();

    Connection conn = SimpleDataSourceV2.getConnection();

    Statement stat = conn.createStatement();

    ResultSet rs = stat.executeQuery("SELECT * FROM dier WHERE rnaam = '" + naam + "';");

    ModelItem item;

    if(rs.next()) {
        do{
           item = new ModelItem();
           item.roepnaam = rs.getString("rnaam");
           item.geslacht = rs.getString("gesl");
           item.snr = rs.getInt("snr");
           dier.addElement(item);
        }while(rs.next());
    }else{
        JOptionPane.showMessageDialog(this, "No data found");
    }
    rs.close();

    stat.close();

    lijst.setModel(dier);

} catch (SQLException e) {
    JOptionPane.showMessageDialog(this, e.getMessage());
}

---

非常感谢你，我的兄弟！