Databases
StackOverflow2013
Postsdbo
POGUI - Java Error While Running
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POGUI - Java Error While Running
    primarykey
    data
    text
    <p>I am creating a Address Book and all the code is done but I keep getting an error! this is the error:</p> <pre><code>Exception in thread "main" java.lang.NullPointerException at java.awt.Container.addImpl(Unknown Source) at java.awt.Container.add(Unknown Source) at javax.swing.JFrame.addImpl(Unknown Source) at java.awt.Container.add(Unknown Source) at MyAddressBook.&lt;init&gt;(MyAddressBook.java:40) at MyAddressBook.main(MyAddressBook.java:31) </code></pre> <p>When I run the address book the error appears and with an empty frame, the frame is not reading the content, Please run the code and you will see what I am talking about. Please suggest How I may Fix This? </p> <p>My Code:</p> <pre><code>import javax.swing.*; import javax.swing.event.DocumentEvent; import javax.swing.event.DocumentListener; import javax.swing.event.ListSelectionEvent; import java.awt.event.*; import java.awt.*; import java.io.*; public class AddressBook { private JLabel lblFirstname,lblSurname, lblMiddlename, lblPhone, lblEmail,lblAddressOne, lblAddressTwo, lblCity, lblPostCode, lblPicture; private JTextField txtFirstName, txtSurname, txtAddressOne, txtPhone, txtMiddlename, txtAddressTwo, txtEmail, txtCity, txtPostCode; private JButton btSave, btExit, btDelete; private JList&lt;String&gt; list; private DefaultListModel&lt;String&gt; listModel; private JPanel panel; PrintWriter out; public static void main(String[] args) throws Exception{ new AddressBook(); } public AddressBook() throws Exception{ JFrame frame = new JFrame("My Address Book"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(900,400); frame.setVisible(true); out = new PrintWriter (new BufferedWriter (new FileWriter("outfile.txt",true))); frame.add(panel); frame.setVisible(true); } public void MyPanel() { panel = new JPanel(); panel.setLayout(null); panel.setBackground(Color.cyan); } public void Fields () { lblFirstname = new JLabel("First name"); lblFirstname.setBounds(135, 50, 150, 20); Font styleOne = new Font("Arial", Font.BOLD, 13); lblFirstname.setFont(styleOne); panel.add(lblFirstname); txtFirstName = new JTextField(); txtFirstName.setBounds(210, 50, 150, 20); panel.add(txtFirstName); lblSurname = new JLabel ("Surname"); lblSurname.setBounds(385,50,150,20); Font styleTwo = new Font ("Arial",Font.BOLD,13); lblSurname.setFont(styleTwo); panel.add(lblSurname); txtSurname = new JTextField(); txtSurname.setBounds(450,50,150,20); panel.add(txtSurname); lblMiddlename = new JLabel ("Middle Name"); lblMiddlename.setBounds(620,50,150,20); Font styleThree = new Font ("Arial", Font.BOLD,13); lblMiddlename.setFont(styleThree); panel.add(lblMiddlename); txtMiddlename = new JTextField(); txtMiddlename.setBounds(710,50,150,20); panel.add(txtMiddlename); lblPhone = new JLabel("Phone"); lblPhone.setBounds(160,100,100,20); Font styleFour = new Font ("Arial", Font.BOLD,13); lblPhone.setFont(styleFour); panel.add(lblPhone); txtPhone = new JTextField(); txtPhone.setBounds(210,100,150,20); panel.add(txtPhone); lblEmail = new JLabel("Email"); lblEmail.setBounds(410,100,100,20); Font styleFive = new Font ("Arial", Font.BOLD,13); lblEmail.setFont(styleFive); panel.add(lblEmail); txtEmail = new JTextField(); txtEmail.setBounds(450,100,150,20); panel.add(txtEmail); lblAddressOne = new JLabel("Address 1"); lblAddressOne.setBounds(145,150,100,20); Font styleSix = new Font ("Arial", Font.BOLD,13); lblAddressOne.setFont(styleSix); panel.add(lblAddressOne); txtAddressOne = new JTextField(); txtAddressOne.setBounds(210,150,150,20); panel.add(txtAddressOne); lblAddressTwo = new JLabel("Address 2"); lblAddressTwo.setBounds(145,200,100,20); Font styleSeven = new Font ("Arial", Font.BOLD,13); lblAddressTwo.setFont(styleSeven); panel.add(lblAddressTwo); txtAddressTwo = new JTextField(); txtAddressTwo.setBounds(210,200,150,20); panel.add(txtAddressTwo); lblCity = new JLabel("City"); lblCity.setBounds(180,250,100,20); Font styleEight = new Font ("Arial", Font.BOLD,13); lblCity.setFont(styleEight); panel.add(lblCity); txtCity = new JTextField(); txtCity.setBounds(210,250,150,20); panel.add(txtCity); lblPostCode = new JLabel("Post Code"); lblPostCode.setBounds(380,250,100,20); Font styleNine = new Font ("Arial", Font.BOLD,13); lblPostCode.setFont(styleNine); panel.add(lblPostCode); txtPostCode = new JTextField(); txtPostCode.setBounds(450,250,150,20); panel.add(txtPostCode); } public void Image() { ImageIcon image = new ImageIcon("icon.png"); lblPicture = new JLabel(image); lblPicture.setBounds(600,90, 330, 270); panel.add(lblPicture); } public void Buttons() { btSave = new JButton ("Save"); btSave.setBounds(380,325,100,20); panel.add(btSave); btSave.addActionListener(new SaveListener(btDelete)); btDelete = new JButton ("Delete"); btDelete.setBounds(260,325,100,20); panel.add(btDelete); btDelete.addActionListener(new DeleteListener()); btExit = new JButton ("Exit"); btExit.setBounds(500,325,100,20); panel.add(btExit); btExit.addActionListener(new Action()); } public void List() { listModel = new DefaultListModel&lt;String&gt;(); listModel.addElement("Daniel Walker"); listModel.addElement("John Smith"); listModel.addElement("Bob Jones"); //JList list = new JList&lt;String&gt;(listModel); list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); list.setSelectedIndex(0); list.setVisibleRowCount(5); list.setBounds(0,10,125,350); panel.add(list); } static class Action implements ActionListener { public void actionPerformed(ActionEvent e) { JFrame option = new JFrame(); int n = JOptionPane.showConfirmDialog(option, "Are you sure you want to exit?", "Exit?", JOptionPane.YES_NO_OPTION); if(n == JOptionPane.YES_OPTION){ System.exit(0); } } } class SaveListener implements ActionListener, DocumentListener { private boolean alreadyEnabled = false; private JButton button; public SaveListener(JButton button) { this.button = button; } //Required by ActionListener. public void actionPerformed(ActionEvent e) { String name = txtFirstName.getText(); //User didn't type in a unique name... if (name.equals("") || alreadyInList(name)) { Toolkit.getDefaultToolkit().beep(); txtFirstName.requestFocusInWindow(); txtFirstName.selectAll(); return; } int index = list.getSelectedIndex(); //get selected index if (index == -1) { //no selection, so insert at beginning index = 0; } else { //add after the selected item index++; } listModel.insertElementAt(txtFirstName.getText() +" "+ txtSurname.getText(), index); //print to file out.println(txtFirstName.getText()); out.println(txtSurname.getText()); out.println(txtMiddlename.getText()); out.println(txtPhone.getText()); out.println(txtAddressOne.getText()); out.println(txtAddressTwo.getText()); out.println(txtEmail.getText()); out.println(txtCity.getText()); out.println(txtPostCode.getText()); out.close(); //Reset the text field. txtFirstName.requestFocusInWindow(); txtSurname.requestFocusInWindow(); txtMiddlename.requestFocusInWindow(); txtPhone.requestFocusInWindow(); txtAddressOne.requestFocusInWindow(); txtAddressTwo.requestFocusInWindow(); txtEmail.requestFocusInWindow(); txtCity.requestFocusInWindow(); txtPostCode.requestFocusInWindow(); txtFirstName.setText(""); txtSurname.setText(""); txtMiddlename.setText(""); txtPhone.setText(""); txtAddressOne.setText(""); txtAddressTwo.setText(""); txtEmail.setText(""); txtCity.setText(""); txtPostCode.setText(""); //Select the new item and make it visible. list.setSelectedIndex(index); list.ensureIndexIsVisible(index); } protected boolean alreadyInList(String name) { return listModel.contains(name); } //Required by DocumentListener. public void insertUpdate(DocumentEvent e) { enableButton(); } //Required by DocumentListener. public void removeUpdate(DocumentEvent e) { handleEmptyTextField(e); } //Required by DocumentListener. public void changedUpdate(DocumentEvent e) { if (!handleEmptyTextField(e)) { enableButton(); } } private void enableButton() { if (!alreadyEnabled) { button.setEnabled(true); } } private boolean handleEmptyTextField(DocumentEvent e) { if (e.getDocument().getLength() &lt;= 0) { button.setEnabled(false); alreadyEnabled = false; return true; } return false; } } public void valueChanged(ListSelectionEvent e) { if (e.getValueIsAdjusting() == false) { if (list.getSelectedIndex() == -1) { btDelete.setEnabled(false); } else { btDelete.setEnabled(true); } } } class DeleteListener implements ActionListener { public void actionPerformed(ActionEvent e) { int index = list.getSelectedIndex(); listModel.remove(index); int size = listModel.getSize(); if (size == 0) { btDelete.setEnabled(false); } else { if (index == listModel.getSize()) { index--; } list.setSelectedIndex(index); list.ensureIndexIsVisible(index); } } } </code></pre> <p>}</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USحسن Chaudhry
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POGUI - Java Error While Running
      1. This table or related slice is empty.
      1. VTDownMod
    2. VO
      singulars
      1. POGUI - Java Error While Running
      1. This table or related slice is empty.
      1. VTDownMod
    3. VO
      singulars
      1. POGUI - Java Error While Running
      1. This table or related slice is empty.
      1. VTDownMod
    1. COCan you make your title more informative please? And you have to point out to the line from which the exception is thrown. Another important thing..post relevant parts only..
      singulars
      1. POGUI - Java Error While Running
      1. USMaroun
    2. COWhich lines are lines 40 and 31? Whatever you're doing, you're trying to use a `null` object as though it were not `null`.
      singulars
      1. POGUI - Java Error While Running
      1. This table or related slice is empty.
    3. COThere is something wrong with the main method that all I could figure out.
      singulars
      1. POGUI - Java Error While Running
      1. USحسن Chaudhry
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload