程序将更新一次，我可以进入并更改表中的内容并点击更新。我可以更新，只要我不退出程序，一旦我再次运行程序，我注意到它保存了我更改的单元格，但它也添加了一行空白单元格。我试图再次更新一些更改它对我的错误：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.io.Writer.write(Writer.java:157)
at testaddress.Testaddress$3.actionPerformed(Testaddress.java:267)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3312)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
它还会擦除我的整个信息文件，留下一个空白的txt文件。 下面是代码：
update.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
try{
BufferedWriter bfw = new BufferedWriter(new FileWriter(tmp));
for (int i = 0 ; i < table.getRowCount(); i++)
{
bfw.newLine();
for(int j = 0 ; j < table.getColumnCount();j++)
{
bfw.write((String)(table.getValueAt(i,j)));
bfw.write("\t");
}
}
bfw.close();
} catch(IOException ea) {
System.out.println(
"Input/Output Exception occurred: " +
ea.getMessage());
}
}});
以下是代码的其余部分：
package testaddress;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
import javax.swing.table.DefaultTableModel;
public class Testaddress extends JFrame {
public static JTable table;
public static DefaultTableModel model;
public static JButton update;
public static File tmp;
public static void MyAddressBook(Container pane) throws FileNotFoundException, IOException{
JLabel Name;
pane.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.fill = GridBagConstraints.HORIZONTAL;
Name = new JLabel("Name:");
gbc.weightx = 0.5;
gbc.gridx = 0;
gbc.gridy = 0;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(Name, gbc);
final JTextField textName = new JTextField();
gbc.weightx = 0.5;
gbc.gridx = 1;
gbc.gridy = 0;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textName, gbc);
JLabel HPhone = new JLabel("Home Phone #:");
gbc.weightx = 0.5;
gbc.gridx = 2;
gbc.gridy = 0;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(HPhone, gbc);
final JTextField textHPhone = new JTextField();
gbc.weightx = 0.5;
gbc.gridx = 3;
gbc.gridy = 0;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textHPhone, gbc);
JLabel CellPhone = new JLabel("Cell Phone #:");
gbc.weightx = 0.5;
gbc.gridx = 0;
gbc.gridy = 1;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(CellPhone, gbc);
final JTextField textCPhone = new JTextField();
gbc.weightx = 0.5;
gbc.gridx = 1;
gbc.gridy = 1;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textCPhone, gbc);
JLabel Address = new JLabel("Address");
gbc.weightx = 0.5;
gbc.gridx = 2;
gbc.gridy = 1;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(Address, gbc);
final JTextField textAddress = new JTextField();
gbc.weightx = 0.5;
gbc.gridx = 3;
gbc.gridy = 1;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textAddress, gbc);
JLabel City = new JLabel("City:");
gbc.weightx = 0.5;
gbc.gridx = 0;
gbc.gridy = 2;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(City, gbc);
final JTextField textCity = new JTextField();
gbc.weightx = 0.5;
gbc.gridx = 1;
gbc.gridy = 2;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textCity, gbc);
JLabel State = new JLabel("State:");
gbc.weightx = 0.5;
gbc.gridx = 2;
gbc.gridy = 2;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(State, gbc);
final JTextField textState = new JTextField();
gbc.weightx = 0.5;
gbc.gridx = 3;
gbc.gridy = 2;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textState, gbc);
JLabel Zip = new JLabel("Zipcode:");
gbc.weighty = 0.1;
gbc.weightx = 0.5;
gbc.gridx = 0;
gbc.gridy = 3;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(Zip, gbc);
final JTextField textZip = new JTextField();
gbc.weighty = 0.1;
gbc.weightx = 0.5;
gbc.gridx = 1;
gbc.gridy = 3;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textZip, gbc);
JLabel Country = new JLabel("Country:");
gbc.weightx = 0.5;
gbc.gridx = 2;
gbc.gridy = 3;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(Country, gbc);
final JTextField textCountry = new JTextField();
gbc.weighty = 0.1;
gbc.weightx = 0.5;
gbc.gridx = 3;
gbc.gridy = 3;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(textCountry, gbc);
update = new JButton("Update");
gbc.weightx = 0.5;
gbc.gridx = 1;
gbc.gridy = 5;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(update, gbc);
JButton exit = new JButton("Exit");
gbc.weightx = 0.5;
gbc.gridx = 3;
gbc.gridy = 5;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(exit, gbc);
exit.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
if (JOptionPane.showConfirmDialog(null, "Do you really want to quit?", "Quit",
JOptionPane.YES_NO_OPTION) == JOptionPane.YES_OPTION)
{
System.exit(0);
}
}
});
JButton save = new JButton("Save");
gbc.weightx = 0.5;
gbc.gridx = 2;
gbc.gridy = 5;
gbc.anchor = GridBagConstraints.NORTH;
pane.add(save, gbc);
JSeparator sep = new JSeparator();
sep.setPreferredSize(new Dimension(5,1));
gbc.weighty = 0.2;
gbc.weightx = 0.5;
gbc.gridx = 0;
gbc.gridy = 7;
gbc.gridwidth = 5;
gbc.anchor = GridBagConstraints.CENTER;
pane.add(sep, gbc);
File fold = new File(System.getProperty("user.home")
+ "/.MyAddressBook");
if(!fold.exists()){
fold.mkdir();
}
tmp = new File(System.getProperty("user.home") +
"/.MyAddressBook/MyAddressBook.txt");
if(!tmp.exists()){
tmp.createNewFile();
}
table = new JTable();
JScrollPane scroll = new JScrollPane(table);
String[] colNames = { "Name:", "Home Phone #:", "Cell Phone #:", "Address",
"City:", "State:", "Zip Code:", "Country:"};
model = new DefaultTableModel(colNames, 0);
final FileInputStream is;
is = new FileInputStream(tmp);
InsertData(is);
gbc.weighty = 1;
gbc.weightx = 0.5;
gbc.gridx = 0;
gbc.gridy = 8;
gbc.gridwidth = 4;
gbc.gridheight = 9;
gbc.anchor = GridBagConstraints.CENTER;
pane.add(new JScrollPane(table), gbc);
save.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
BufferedWriter writer;
try {
writer = new BufferedWriter(new FileWriter(tmp,true));
writer.write(textName.getText() + "\t" + textHPhone.getText()
+ "\t" + textCPhone.getText() + "\t" + textAddress.getText() + "\t"
+ textCity.getText() + "\t" + textState.getText() + "\t" +
textZip.getText() + "\t" + textCountry.getText());
writer.newLine();
writer.close();
} catch(FileNotFoundException ex) {
} catch (IOException ex) {
}
Scanner scan = new Scanner(is);
String[] array;
while (scan.hasNextLine()) {
String line = scan.nextLine();
if(line.indexOf("\t")>-1)
array = line.split("\t");
else
array = line.split("\t");
Object[] data = new Object[array.length];
for (int i = 0; i < array.length; i++)
data[i] = array[i];
model.addRow(data);
}
table.setModel(model);
}});
update.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
try{
BufferedWriter bfw = new BufferedWriter(new FileWriter(tmp));
for (int i = 0 ; i < table.getRowCount(); i++)
{
bfw.newLine();
for(int j = 0 ; j < table.getColumnCount();j++)
{
bfw.write((String)(table.getValueAt(i,j)));
bfw.write("\t");;
}
}
bfw.close();
} catch(IOException ea) {
System.out.println(
"Input/Output Exception occurred: " +
ea.getMessage());
}
}});
}
public static void InsertData(FileInputStream is){
Scanner scan = new Scanner(is);
String[] array;
while (scan.hasNextLine()) {
String line = scan.nextLine();
if(line.indexOf(",")>-1)
array = line.split(",");
else
array = line.split("\t");
Object[] data = new Object[array.length];
System.arraycopy(array, 0, data, 0, array.length);
model.addRow(data);
}
table.setModel(model);
}
public static void main(String[] args) throws FileNotFoundException, IOException {
JFrame frame = new Testaddress();
frame.setTitle("My Address Book");
frame.setSize(900, 600);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MyAddressBook(frame.getContentPane());
frame.setVisible(true);
}
}
是什么导致第267行为空，我该如何解决这个问题？
答案 0 :(得分：1)
Testadress.java中哪一行是267？ 我敢打赌这是这样的：
bfw.write((String)(table.getValueAt(i,j)));
所以我猜table.getValueAt(i,j)会返回null，演员会带来NullPointerException
但是如果不了解您的代码，就无法提供帮助。
<强>更新
您将覆盖整个文件。如果你想追加，你必须pass true as second parameter：
new FileWriter(tmp, true);