Java 当我单击AddStudent时，程序冻结

数据库连接类（SmartData）

增加新的学生班级

package smartdatabase;

/**
 *
 * @author travi
 */
public class AddStudent extends javax.swing.JFrame {
private        Conn con = new Conn();
    /**
     * Creates new form AddStudent
     */
    public AddStudent() {
        initComponents();
         int i=0;
         while(con.getCentreNamebyCid(i)!=null){
         jcbCentre.addItem(con.getCentreNamebyCid(i));
         i++;
    }
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        lblTitle = new javax.swing.JLabel();
        lblFirstName = new javax.swing.JLabel();
        lblSurname = new javax.swing.JLabel();
        lblCentre = new javax.swing.JLabel();
        lblKids = new javax.swing.JLabel();
        txbFirstName = new javax.swing.JTextField();
        txbSurname = new javax.swing.JTextField();
        jfcPDF = new javax.swing.JFileChooser();
        jcbCentre = new javax.swing.JComboBox<>();
        jcbKids = new javax.swing.JComboBox<>();
        btnCancel = new javax.swing.JButton();
        jLabel6 = new javax.swing.JLabel();
        btnAdd = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        lblTitle.setText("Add new student");

        lblFirstName.setText("First Name:");

        lblSurname.setText("Surname:");

        lblCentre.setText("Centre:");

        lblKids.setText("Class:");

        jfcPDF.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jfcPDFActionPerformed(evt);
            }
        });

        btnCancel.setText("Cancel");

        jLabel6.setText("Please select the PDF containing the student's documents");

        btnAdd.setText("Add Student");
        btnAdd.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnAddActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(109, 109, 109)
                        .addComponent(jfcPDF, javax.swing.GroupLayout.PREFERRED_SIZE, 486, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(btnAdd))
                    .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
                        .addComponent(btnCancel))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(191, 191, 191)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                                .addComponent(lblTitle, javax.swing.GroupLayout.PREFERRED_SIZE, 90, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGroup(layout.createSequentialGroup()
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                        .addComponent(lblFirstName)
                                        .addComponent(lblSurname, javax.swing.GroupLayout.Alignment.TRAILING)
                                        .addComponent(lblCentre, javax.swing.GroupLayout.Alignment.TRAILING)
                                        .addComponent(lblKids, javax.swing.GroupLayout.Alignment.TRAILING))
                                    .addGap(31, 31, 31)
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                                        .addComponent(txbFirstName, javax.swing.GroupLayout.Alignment.LEADING)
                                        .addComponent(txbSurname, javax.swing.GroupLayout.Alignment.LEADING)
                                        .addComponent(jcbCentre, javax.swing.GroupLayout.Alignment.LEADING, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                        .addComponent(jcbKids, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.PREFERRED_SIZE, 135, javax.swing.GroupLayout.PREFERRED_SIZE))))
                            .addComponent(jLabel6))))
                .addContainerGap(12, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(lblTitle)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblFirstName)
                    .addComponent(txbFirstName, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblSurname)
                    .addComponent(txbSurname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblCentre)
                    .addComponent(jcbCentre, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblKids)
                    .addComponent(jcbKids, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 36, Short.MAX_VALUE)
                .addComponent(jLabel6)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jfcPDF, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(btnAdd))
                .addGap(0, 0, 0)
                .addComponent(btnCancel)
                .addContainerGap())
        );

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

    private void jfcPDFActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
    }                                      

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

        con.addStudent(txbFirstName.getText(),txbSurname.getText(),1);
    }                                      

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new AddStudent().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton btnAdd;
    private javax.swing.JButton btnCancel;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JComboBox<String> jcbCentre;
    private javax.swing.JComboBox<String> jcbKids;
    private javax.swing.JFileChooser jfcPDF;
    private javax.swing.JLabel lblCentre;
    private javax.swing.JLabel lblFirstName;
    private javax.swing.JLabel lblKids;
    private javax.swing.JLabel lblSurname;
    private javax.swing.JLabel lblTitle;
    private javax.swing.JTextField txbFirstName;
    private javax.swing.JTextField txbSurname;
    // End of variables declaration                   
}

封装智能数据库；
/**
*
*@作者特拉维
*/
公共类AddStudent扩展javax.swing.JFrame{
专用连接con=新连接（）；
/**
*创建新的表单AddStudent
*/
公立学校学生（）{
初始化组件（）；
int i=0；
while（con.getCentreNamebyCid（i）！=null）{
jcbcenter.addItem（con.getCentreNamebyCid（i））；
i++；
}
}
@抑制警告（“未选中”）
//                           
私有组件（）{
lblTitle=newjavax.swing.JLabel（）；
lblFirstName=newjavax.swing.JLabel（）；
lblSurname=newjavax.swing.JLabel（）；
lblCentre=newjavax.swing.JLabel（）；
lblKids=newjavax.swing.JLabel（）；
txbFirstName=newjavax.swing.JTextField（）；
txb姓氏=newjavax.swing.JTextField（）；
jfcPDF=newjavax.swing.JFileChooser（）；
jcbCentre=newjavax.swing.JComboBox（）；
jcbKids=newjavax.swing.JComboBox（）；
btnCancel=newjavax.swing.JButton（）；
jLabel6=newjavax.swing.JLabel（）；
btnAdd=newjavax.swing.JButton（）；
setDefaultCloseOperation（javax.swing.WindowConstants.EXIT_ON_CLOSE）；
lblTitle.setText（“添加新学生”）；
lblFirstName.setText（“名字：”）；
lblSurname.setText（“姓氏：”）；
lblCentre.setText（“中心：”）；
lblKids.setText（“类：”）；
jfcPDF.addActionListener（新java.awt.event.ActionListener（）{
public void actionPerformed（java.awt.event.ActionEvent evt）{
jfcpdt（evt）；
}
});
btnCancel.setText（“取消”）；
jLabel6.setText（“请选择包含学生文档的PDF”）；
btnAdd.setText（“添加学生”）；
addActionListener（新java.awt.event.ActionListener（）{
public void actionPerformed（java.awt.event.ActionEvent evt）{
执行的BTNADDACION（evt）；
}
});
javax.swing.GroupLayout=newjavax.swing.GroupLayout（getContentPane（））；
getContentPane（）.setLayout（布局）；
layout.setHorizontalGroup(
createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createSequentialGroup（）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createSequentialGroup（）
.addGap（109、109、109）
.addComponent（jfcPDF，javax.swing.GroupLayout.PREFERRED\u SIZE，486，javax.swing.GroupLayout.PREFERRED\u SIZE）
.addGap（18,18,18）
.addComponent（btnAdd））
.addGroup（layout.createSequentialGroup（）
.addContainerGap（）
.addComponent（btnCancel））
.addGroup（layout.createSequentialGroup（）
.addGap（191191191191）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.training）
.addComponent（lbltle，javax.swing.GroupLayout.PREFERRED\u SIZE，90，javax.swing.GroupLayout.PREFERRED\u SIZE）
.addGroup（layout.createSequentialGroup（）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addComponent（lblFirstName）
.addComponent（lblSurname、javax.swing.GroupLayout.Alignment.training）
.addComponent（lblCentre、javax.swing.GroupLayout.Alignment.training）
.addComponent（lblKids、javax.swing.GroupLayout.Alignment.training））
.addGap（31,31,31）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.training，false）
.addComponent（txbFirstName、javax.swing.GroupLayout.Alignment.LEADING）
.addComponent（txbNames，javax.swing.GroupLayout.Alignment.LEADING）
.addComponent（jcbcenter，javax.swing.GroupLayout.Alignment.LEADING，0，javax.swing.GroupLayout.DEFAULT\u SIZE，Short.MAX\u值）
.addComponent（jcbKids，javax.swing.GroupLayout.Alignment.LEADING，javax.swing.GroupLayout.PREFERRED_SIZE，135，javax.swing.GroupLayout.PREFERRED_SIZE）））
.addComponent（jLabel6）））
.addContainerGap（12，简称最大值））
);
layout.setVerticalGroup(
createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createSequentialGroup（）
.addContainerGap（）
.addComponent（lblTitle）
.addGap（18,18,18）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.BASELINE）
.addComponent（lblFirstName）
.addComponent（txbFirstName、javax.swing.GroupLayout.PREFERRED_SIZE、javax.swing.GroupLayout.DEFAULT_SIZE、javax.swing.GroupLayout.PREFERRED_SIZE））
.addGap（18,18,18）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.BASELINE）
.addComponent（lblSurname）
.addComponent（txbNames，javax.swing.GroupLayout.PREFERRED\u SIZE，javax.swing.GroupLayout.DEFAULT\u SIZE，javax.swing.GroupLayout.PREFERRED\u SIZE））
.addGap（18,18,18）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.BASELINE）
package smartdatabase;

/**
 *
 * @author travi
 */
public class AddStudent extends javax.swing.JFrame {
private        Conn con = new Conn();
    /**
     * Creates new form AddStudent
     */
    public AddStudent() {
        initComponents();
         int i=0;
         while(con.getCentreNamebyCid(i)!=null){
         jcbCentre.addItem(con.getCentreNamebyCid(i));
         i++;
    }
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        lblTitle = new javax.swing.JLabel();
        lblFirstName = new javax.swing.JLabel();
        lblSurname = new javax.swing.JLabel();
        lblCentre = new javax.swing.JLabel();
        lblKids = new javax.swing.JLabel();
        txbFirstName = new javax.swing.JTextField();
        txbSurname = new javax.swing.JTextField();
        jfcPDF = new javax.swing.JFileChooser();
        jcbCentre = new javax.swing.JComboBox<>();
        jcbKids = new javax.swing.JComboBox<>();
        btnCancel = new javax.swing.JButton();
        jLabel6 = new javax.swing.JLabel();
        btnAdd = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        lblTitle.setText("Add new student");

        lblFirstName.setText("First Name:");

        lblSurname.setText("Surname:");

        lblCentre.setText("Centre:");

        lblKids.setText("Class:");

        jfcPDF.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jfcPDFActionPerformed(evt);
            }
        });

        btnCancel.setText("Cancel");

        jLabel6.setText("Please select the PDF containing the student's documents");

        btnAdd.setText("Add Student");
        btnAdd.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnAddActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(109, 109, 109)
                        .addComponent(jfcPDF, javax.swing.GroupLayout.PREFERRED_SIZE, 486, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(btnAdd))
                    .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
                        .addComponent(btnCancel))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(191, 191, 191)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                                .addComponent(lblTitle, javax.swing.GroupLayout.PREFERRED_SIZE, 90, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGroup(layout.createSequentialGroup()
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                        .addComponent(lblFirstName)
                                        .addComponent(lblSurname, javax.swing.GroupLayout.Alignment.TRAILING)
                                        .addComponent(lblCentre, javax.swing.GroupLayout.Alignment.TRAILING)
                                        .addComponent(lblKids, javax.swing.GroupLayout.Alignment.TRAILING))
                                    .addGap(31, 31, 31)
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                                        .addComponent(txbFirstName, javax.swing.GroupLayout.Alignment.LEADING)
                                        .addComponent(txbSurname, javax.swing.GroupLayout.Alignment.LEADING)
                                        .addComponent(jcbCentre, javax.swing.GroupLayout.Alignment.LEADING, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                        .addComponent(jcbKids, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.PREFERRED_SIZE, 135, javax.swing.GroupLayout.PREFERRED_SIZE))))
                            .addComponent(jLabel6))))
                .addContainerGap(12, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(lblTitle)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblFirstName)
                    .addComponent(txbFirstName, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblSurname)
                    .addComponent(txbSurname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblCentre)
                    .addComponent(jcbCentre, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblKids)
                    .addComponent(jcbKids, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 36, Short.MAX_VALUE)
                .addComponent(jLabel6)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jfcPDF, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(btnAdd))
                .addGap(0, 0, 0)
                .addComponent(btnCancel)
                .addContainerGap())
        );

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

    private void jfcPDFActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
    }                                      

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

        con.addStudent(txbFirstName.getText(),txbSurname.getText(),1);
    }                                      

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(AddStudent.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new AddStudent().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton btnAdd;
    private javax.swing.JButton btnCancel;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JComboBox<String> jcbCentre;
    private javax.swing.JComboBox<String> jcbKids;
    private javax.swing.JFileChooser jfcPDF;
    private javax.swing.JLabel lblCentre;
    private javax.swing.JLabel lblFirstName;
    private javax.swing.JLabel lblKids;
    private javax.swing.JLabel lblSurname;
    private javax.swing.JLabel lblTitle;
    private javax.swing.JTextField txbFirstName;
    private javax.swing.JTextField txbSurname;
    // End of variables declaration                   
}


String getCentreNamebyCid(int i) {
   String out;
   try {
   ...