所以我编写了这个程序，此刻，所有的按钮都按照我的要求去做，但是出现了很多运行时错误。以下是整个文字的链接：http://pastie.org/9488033#6,16-17
deleteClient.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent arg0){
//panel info
JPanel panel2 = new JPanel();
panel2.setLayout(new GridBagLayout());
GridBagConstraints d = new GridBagConstraints();
d.fill = GridBagConstraints.HORIZONTAL;
//frame
JFrame frame2 = new JFrame("Remove Client");
//text area for waiting number
final JTextArea waitingNumberArea = new JTextArea("Enter clients waiting number you wish to remove");
JScrollPane scroll4 = new JScrollPane(waitingNumberArea);
d.ipadx = 60;
d.ipady = 20;
d.gridwidth = 1;
d.gridx = 0;
d.gridy = 0;
panel2.add(scroll4, d);
//text area for name
final JTextArea nameTextArea = new JTextArea("Enter client name");
JScrollPane scroll3 = new JScrollPane(nameTextArea);
d.ipadx = 60;
d.ipady = 20;
d.gridwidth = 1;
d.gridx = 0;
d.gridy = 1;
panel2.add(scroll3, d);
//text area for surname
final JTextArea surnameTextArea = new JTextArea("Enter client surname");
JScrollPane scroll2 = new JScrollPane(surnameTextArea);
d.ipadx = 60;
d.ipady = 20;
d.gridwidth = 1;
d.gridx = 0;
d.gridy = 2;
panel2.add(scroll2, d);
//text area for number
final JTextArea numberTextArea = new JTextArea("Enter client number");
JScrollPane scroll1 = new JScrollPane(numberTextArea);
d.ipadx = 60;
d.ipady = 20;
d.gridwidth = 1;
d.gridx = 0;
d.gridy = 3;
panel2.add(scroll1, d);
//button to add client
JButton removeClient = new JButton("Remove Client");
d.ipadx = 0;
d.ipady = 90;
d.gridwidth = 1;
d.gridheight = 4;
d.gridx = 1;
d.gridy = 0;
panel2.add(removeClient, d);
//frame settings
frame2.setVisible(true);
frame2.setLocationRelativeTo(null);
frame2.add(panel2);
frame2.pack();
frame2.setResizable(false);
removeClient.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent arg0){
final String waitingNumber = waitingNumberArea.getText();
final String clientName = nameTextArea.getText();
final String clientSurname = surnameTextArea.getText();
final String clientNumber = numberTextArea.getText();
int rows = 20;
int columns = 4;
int g;
for (int r = 0; r < rows ; r++ )
{
if (clientsArray[r][0].equals (waitingNumber))
for (int i = 0; i < 4 ; i++ )
{
tableModel.setValueAt("", r, i);
clientsArray[r][i] = ("0");
}
}
}
});
}
});
一切正常，但会出现这些运行时错误
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at jTableTest$3$1.actionPerformed(jTableTest.java:390)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:20
22)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.jav
a:2346)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259
)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6527)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6292)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4883)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898
)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDo
main.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDo
main.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:719)
at java.awt.EventQueue$4.run(EventQueue.java:717)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDo
main.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)