我试图自己解决这个问题，但我不知道如何解决这个问题。
当我尝试运行 addressBookUi 类时出现此错误。
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at addressBookUI.startComponents(addressBookUI.java:43)
at addressBookUI.<init>(addressBookUI.java:6)
at addressBookUI$2.run(addressBookUI.java:143)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
这是我的地址BookUi类
import javax.swing.table.DefaultTableModel;
public class addressBookUI extends javax.swing.JFrame {
public addressBookUI() {
startComponents();
}
private void startComponents() {
mainScrollPane = new javax.swing.JScrollPane();
mainTable = new javax.swing.JTable();
addButton = new javax.swing.JButton();
saveButton = new javax.swing.JButton();
deleteButton = new javax.swing.JButton();
mainMenuBar = new javax.swing.JMenuBar();
mainMenu = new javax.swing.JMenu();
newMenuItem = new javax.swing.JMenuItem();
openMenuItem = new javax.swing.JMenuItem();
saveMenuItem = new javax.swing.JMenuItem();
printMenuItem = new javax.swing.JMenuItem();
quitMenuItem = new javax.swing.JMenuItem();
editMenuBar = new javax.swing.JMenu();
editPersonsMenuItem = new javax.swing.JMenuItem();
sortNameMenuItem = new javax.swing.JMenuItem();
sortPostcodeMenuItem = new javax.swing.JMenuItem();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
mainTable.setModel(new javax.swing.table.DefaultTableModel(
new Object[][] { { null, null, null, null },
{ null, null, null, null }, { null, null, null, null },
{ null, null, null, null } }, new String[] { "Title 1",
"Title 2", "Title 3", "Title 4" }));
mainScrollPane.setViewportView(mainTable);
addButton.setText("Add");
saveButton.setText("Save Row");
deleteButton.setText("Delete Row");
refreshButton.setText("Refresh");
refreshButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
refreshButtonActionPerformed(evt);
}
});
mainMenu.setText("File");
newMenuItem.setText("New");
mainMenu.add(newMenuItem);
openMenuItem.setText("Open");
saveMenuItem.setText("Save");
mainMenu.add(saveMenuItem);
printMenuItem.setText("Print");
mainMenu.add(printMenuItem);
quitMenuItem.setText("Quit");
mainMenu.add(quitMenuItem);
mainMenuBar.add(mainMenu);
editMenuBar.setText("Edit");
editPersonsMenuItem.setText("Edit Selected Persons");
editMenuBar.add(editPersonsMenuItem);
sortNameMenuItem.setText("Sort by Name");
editMenuBar.add(sortNameMenuItem);
sortPostcodeMenuItem.setText("Sort by Postcode");
editMenuBar.add(sortPostcodeMenuItem);
mainMenuBar.add(editMenuBar);
// mainMenuBar.add(helpMenuBar);
setJMenuBar(mainMenuBar);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(
getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(layout
.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(mainScrollPane)
.addGroup(
layout.createSequentialGroup()
.addContainerGap()
.addComponent(addButton,
javax.swing.GroupLayout.PREFERRED_SIZE,
155,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addComponent(saveButton,
javax.swing.GroupLayout.PREFERRED_SIZE,
155,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addComponent(deleteButton,
javax.swing.GroupLayout.PREFERRED_SIZE,
155,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addComponent(refreshButton,
javax.swing.GroupLayout.PREFERRED_SIZE,
155,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(51, Short.MAX_VALUE)));
layout.setVerticalGroup(layout
.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(
layout.createSequentialGroup()
.addComponent(mainScrollPane,
javax.swing.GroupLayout.PREFERRED_SIZE,
163,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(
javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addGroup(
layout.createParallelGroup(
javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(addButton)
.addComponent(saveButton)
.addComponent(deleteButton)
.addComponent(refreshButton))
.addGap(0, 17, Short.MAX_VALUE)));
pack();
}
private void refreshButtonActionPerformed(java.awt.event.ActionEvent evt) {// GEN-FIRST:event_refreshButtonActionPerformed
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new addressBookUI().setVisible(true);
}
});
}
// protected javax.swing.JMenuItem aboutHelpMenuBar;
protected javax.swing.JButton addButton;
protected javax.swing.JButton deleteButton;
private javax.swing.JMenu editMenuBar;
protected javax.swing.JMenuItem editPersonsMenuItem;
private javax.swing.JMenu mainMenu;
// private javax.swing.JMenu helpMenuBar;
private javax.swing.JScrollPane mainScrollPane;
private javax.swing.JMenuBar mainMenuBar;
protected javax.swing.JTable mainTable;
protected javax.swing.JMenuItem newMenuItem;
protected javax.swing.JMenuItem openMenuItem;
protected javax.swing.JMenuItem printMenuItem;
protected javax.swing.JMenuItem quitMenuItem;
protected javax.swing.JButton refreshButton;
protected javax.swing.JButton saveButton;
protected javax.swing.JMenuItem saveMenuItem;
protected javax.swing.JMenuItem sortNameMenuItem;
protected javax.swing.JMenuItem sortPostcodeMenuItem;
}
如果有人可以提供帮助，那就太好了