Java验证

Question

I have a Form with a few textfields and a save button. When the buttton is pressed, it should be checked whether certain textfields are empty, and if those are empty, then an error message should be displayed, else whatever job needed should be performed. i have written the code for that, but whether the fields are empty or not, it performs the main tasks. Could someone advise please? thanks

final JButton button = new JButton("Save");
button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if(textField_2.equals("") || textField_3.equals("") || textField_4.equals("") || textField_5.equals("") || textField_6.equals("") || textArea.equals("") || textField_7.equals("")) {
            JOptionPane.showMessageDialog(frmModifyBooking, "Please fill in all fields indicated with a star (*).");
        }
        else {
            try {
                String sql = "UPDATE vacation SET `StaffID` =?, `From` =?, `To` =?, `TotalDays` =?, `VacationType` =?, `Notes` =?, `Signature` =?, `Date` =? WHERE VacationID = ?";
                PreparedStatement prest = con.prepareStatement(sql);
                prest.setString(1, textField_1.getText());
                prest.setString(2, textField_2.getText());
                prest.setString(3, textField_3.getText());
                prest.setString(4, textField_4.getText());
                prest.setString(5, textField_5.getText());
                prest.setString(6, textArea.getText());
                prest.setString(7, textField_6.getText());
                prest.setString(8, textField_7.getText());
                prest.setString(9, txtAUniqueStudent.getText());
                prest.executeUpdate();
                JOptionPane.showMessageDialog(frmModifyBooking, "Record has been updated.");
            }
            catch (SQLException e) {
                //System.out.println("Record couldn't be added!");
                e.printStackTrace();
                JOptionPane.showMessageDialog(frmModifyBooking, "Record couldn't be updated. Please try again.");
            }
        }
    }
});
button.setBounds(280, 402, 89, 23);
panel_1.add(button);

Answer 1

With textField_2.equals("") you are comparing the object not the JTextFields text.

Simply use:

textField_2.getText().equals("")...

Answer 2

Did you mean:

textField_2.getText().equals("") etc.

which you could also write:

textField_2.getText().isEmpty() etc.

Answer 3

I feel like it's because you're comparing an entire FIELD to the empty string. Try comparing the values instead.

if (textField_1.getText().equals(''))