非法启动Netbeans swing类型错误

Question

我想插入以下代码，以便在单击jTable行(行选择)时完成某些操作。我将这段代码插入到所有方法和块之外，但是它显示了以下错误-"包模型不存在，预期的，非法的类型开始"。

代码,

ListSelectionModel model = expense_table.getSelectionModel();  
  model.addListSelectionListener(new ListSelectionListener(){
        public void valueChanged(ListSelectionEvent event) {
            // do some actions here, for example
            // print first column value from selected row
        }
    });

完整代码,

package finance;
import java.awt.List;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.sql.Statement;
import javax.swing.JOptionPane;
import java.sql.*;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JTable;
import javax.swing.ListSelectionModel;
import javax.swing.table.DefaultTableModel;
/**
 *
 * @author Dell 50
 */
public class DailyTransactions extends javax.swing.JFrame {

    public DailyTransactions() {
        initComponents();
    }

    public static void main(String args[]) {
            /* Set the Nimbus look and feel */
            //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
            /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
             * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
             */
            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(DailyTransactions.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (InstantiationException ex) {
                java.util.logging.Logger.getLogger(DailyTransactions.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (IllegalAccessException ex) {
                java.util.logging.Logger.getLogger(DailyTransactions.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (javax.swing.UnsupportedLookAndFeelException ex) {
                java.util.logging.Logger.getLogger(DailyTransactions.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            }
            //</editor-fold>
            //</editor-fold>
            //</editor-fold>
            //</editor-fold>
            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    new DailyTransactions().setVisible(true);
                }
            });
        }
        // Variables declaration - do not modify                     
        private javax.swing.JButton DeleteBtn;
        private javax.swing.JButton Delete_t;
        private javax.swing.JButton UpdateBtn;
        private javax.swing.JButton addBtn;
        private javax.swing.JComboBox d_date;
        private javax.swing.JComboBox d_month;
        private javax.swing.JComboBox d_year;
        private javax.swing.JTextField daily_total;
        private javax.swing.JComboBox description_menu;
        private javax.swing.JTable expense_table;
        private javax.swing.JTextField id;
        private javax.swing.JTextField id_amount;
        private javax.swing.JButton jButton1;
        private javax.swing.JButton jButton12;
        private javax.swing.JButton jButton13;
        private javax.swing.JButton jButton2;
        private javax.swing.JButton jButton4;
        private javax.swing.JButton jButton5;
        private javax.swing.JButton jButton6;
        private javax.swing.JButton jButton7;
        private javax.swing.JButton jButton8;
        private javax.swing.JButton jButton9;
        private javax.swing.JComboBox jComboBox1;
        private javax.swing.JComboBox jComboBox10;
        private javax.swing.JComboBox jComboBox2;
        private javax.swing.JComboBox jComboBox3;
        private javax.swing.JComboBox jComboBox4;
        private javax.swing.JComboBox jComboBox6;
        private com.toedter.calendar.JDateChooser jDateChooser1;
        private javax.swing.JLabel jLabel1;
        private javax.swing.JLabel jLabel10;
        private javax.swing.JLabel jLabel11;
        private javax.swing.JLabel jLabel12;
        private javax.swing.JLabel jLabel13;
        private javax.swing.JLabel jLabel14;
        private javax.swing.JLabel jLabel15;
        private javax.swing.JLabel jLabel17;
        private javax.swing.JLabel jLabel18;
        private javax.swing.JLabel jLabel2;
        private javax.swing.JLabel jLabel20;
        private javax.swing.JLabel jLabel23;
        private javax.swing.JLabel jLabel3;
        private javax.swing.JLabel jLabel4;
        private javax.swing.JLabel jLabel5;
        private javax.swing.JLabel jLabel6;
        private javax.swing.JLabel jLabel7;
        private javax.swing.JLabel jLabel8;
        private javax.swing.JLabel jLabel9;
        private javax.swing.JMenu jMenu1;
        private javax.swing.JPanel jPanel1;
        private javax.swing.JPanel jPanel2;
        private javax.swing.JPanel jPanel3;
        private javax.swing.JPanel jPanel4;
        private javax.swing.JPanel jPanel5;
        private javax.swing.JPanel jPanel6;
        private javax.swing.JScrollPane jScrollPane1;
        private javax.swing.JScrollPane jScrollPane2;
        private javax.swing.JScrollPane jScrollPane3;
        private javax.swing.JScrollPane jScrollPane4;
        private javax.swing.JTable jTable1;
        private javax.swing.JTable jTable2;
        private javax.swing.JTextField jTextField1;
        private javax.swing.JTextField other_amount;
        private javax.swing.JTextField other_expense;
        private javax.swing.JTextField total_amount;
        private javax.swing.JTabbedPane trans_tab;
        private javax.swing.JTable trans_table;
        // End of variables declaration                   

        ListSelectionModel model = expense_table.getSelectionModel();  
      model.addListSelectionListener(new ListSelectionListener(){
            public void valueChanged(ListSelectionEvent event) {
                // do some actions here, for example
                // print first column value from selected row
            }
        });
    }

如何解决这个问题。我试了几个小时，但还是找不到问题。请帮助。

Answer 1

model.addListSelectionListener(new ListSelectionListener(){
    public void valueChanged(ListSelectionEvent event) {
        // do some actions here, for example
        // print first column value from selected row
    }
});

块必须被{和}包围。或者，将其放入构造函数中。纯可执行语句(即非表达式)必须驻留在语句块中。