我正在为我的学术目的开发一个软件。为此我使用的是Netbeans IDE，sqlite。当我运行代码时，它会给我以下错误，
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1838)
at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.lang.Double.parseDouble(Double.java:538)
at ProductInfo.getProductList(ProductInfo.java:109)
at ProductInfo.Show_Products_In_JTable(ProductInfo.java:126)
at ProductInfo.<init>(ProductInfo.java:44)
at ProductInfo$12.run(ProductInfo.java:658)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.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)
这是代码，
import java.awt.Image;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JOptionPane;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.table.DefaultTableModel;
public class ProductInfo extends javax.swing.JFrame {
Connection conn=null;
ResultSet rs = null;
PreparedStatement pst=null;
public ProductInfo() {
initComponents();
conn=JavaConnect.ConnectDb();
Show_Products_In_JTable();
}
String imgpath=null;
int pos = 0;
public boolean checkInputs()
{
if(
txt_name.getText() == null
|| txt_price.getText() == null
|| txt_AddDate.getSelectedDate().getTime() == null
){
return false;
}
else{
try{
Double.parseDouble(txt_price.getText());
return true;
}catch(Exception ex)
{
return false;
}
}
}
ImageIcon ResizeImage(String imagePath, byte[] pic)
{
ImageIcon myImage = null;
if(imagePath != null)
{
myImage = new ImageIcon(imagePath);
}else{
myImage = new ImageIcon(pic);
}
Image img = myImage.getImage();
Image img2 = img.getScaledInstance(lbl_img.getWidth(), lbl_img.getHeight(), Image.SCALE_SMOOTH);
ImageIcon image = new ImageIcon(img2);
return image;
}
public ArrayList<Product> getProductList()
{
ArrayList<Product> productList = new ArrayList<Product>();
Connection conn=JavaConnect.ConnectDb();;
ResultSet rs;
PreparedStatement pst;
try {
String sql = "SELECT * FROM ProductInfo";
pst=conn.prepareStatement(sql);
rs=pst.executeQuery();
Product product;
while(rs.next())
{
product = new Product(rs.getInt("ProductId"),rs.getString("Name"),Double.parseDouble(rs.getString("Price")),rs.getString("Date"),rs.getBytes("Image"));
productList.add(product);
}
} catch (SQLException ex) {
Logger.getLogger(ProductInfo.class.getName()).log(Level.SEVERE, null, ex);
}
return productList;
}
public void Show_Products_In_JTable()
{
ArrayList<Product> list = getProductList();
DefaultTableModel model = (DefaultTableModel)JTable_Products.getModel();
// clear jtable content
model.setRowCount(0);
Object[] row = new Object[4];
for(int i = 0; i < list.size(); i++)
{
row[0] = list.get(i).getId();
row[1] = list.get(i).getName();
row[2] = list.get(i).getPrice();
row[3] = list.get(i).getAddDate();
model.addRow(row);
}
}
public void ShowItem(int index)
{
txt_id.setText(Integer.toString(getProductList().get(index).getId()));
txt_name.setText(getProductList().get(index).getName());
txt_price.setText(Double.toString(getProductList().get(index).getPrice()));
try {
Date addDate = null;
addDate = new SimpleDateFormat("yyyy-MM-dd").parse((String)getProductList().get(index).getAddDate());
txt_AddDate.getSelectedDate().setTime(addDate);
} catch (ParseException ex) {
Logger.getLogger(ProductInfo.class.getName()).log(Level.SEVERE, null, ex);
}
lbl_image.setIcon(ResizeImage(null, getProductList().get(index).getImage()));
}
private void btn_deleteActionPerformed(java.awt.event.ActionEvent evt) {
if(!txt_id.getText().equals(""))
{
try {
String sql = "DELETE FROM ProductInfo WHERE ProductId = ? ";
pst=conn.prepareStatement(sql);
pst.execute();
int id = Integer.parseInt(txt_id.getText());
pst.setInt(1, id);
pst.executeUpdate();
Show_Products_In_JTable();
JOptionPane.showMessageDialog(null, "Product Deleted");
}
catch (SQLException ex) {
Logger.getLogger(ProductInfo.class.getName()).log(Level.SEVERE, null, ex);
JOptionPane.showMessageDialog(null, "Product Not Deleted");
}
}else{
JOptionPane.showMessageDialog(null, "Product Not Deleted : No Id To Delete");
}
}
private void btn_insertActionPerformed(java.awt.event.ActionEvent evt) {
if(checkInputs() && imgpath != null)
{
try {
String sql = "INSERT INTO ProductInfo(Name,Price,Date,Image) values(?,?,?,?) ";
pst=conn.prepareStatement(sql);
pst.execute();
pst.setString(1, txt_name.getText());
pst.setString(2, txt_price.getText());
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
String addDate = dateFormat.format(txt_AddDate.getSelectedDate().getTime());
pst.setDate(3, java.sql.Date.valueOf(addDate));
InputStream img = new FileInputStream(new File(imgpath));
pst.setBlob(4, img);
pst.executeUpdate();
Show_Products_In_JTable();
JOptionPane.showMessageDialog(null, "Data Inserted");
} catch (Exception ex) {
JOptionPane.showMessageDialog(null, ex.getMessage());
}
}else{
JOptionPane.showMessageDialog(null, "One Or More Field Are Empty");
}
System.out.println("Name => "+txt_name.getText());
System.out.println("Price => "+txt_price.getText());
System.out.println("Date => "+txt_AddDate.getSelectedDate().getTime());
System.out.println("Image => "+imgpath);
}
private void btn_ImageActionPerformed(java.awt.event.ActionEvent evt) {
JFileChooser file = new JFileChooser();
file.setCurrentDirectory(new File(System.getProperty("user.home")));
FileNameExtensionFilter filter = new FileNameExtensionFilter("*.images", "jpg","png");
file.addChoosableFileFilter(filter);
int result = file.showSaveDialog(null);
if(result == JFileChooser.APPROVE_OPTION)
{
File selectedFile = file.getSelectedFile();
String path = selectedFile.getAbsolutePath();
lbl_img.setIcon(ResizeImage(path, null));
imgpath = path;
}
else{
System.out.println("No File Selected");
}
}
private void btn_updateActionPerformed(java.awt.event.ActionEvent evt) {
if(checkInputs() && txt_id.getText() != null)
{
// update without image
if(imgpath == null)
{
try {
String sql = "UPDATE ProductInfo SET Name = ?, Price = ?"
+ ", Date = ? WHERE ProductId = ?";
pst=conn.prepareStatement(sql);
pst.execute();
pst.setString(1, txt_name.getText());
pst.setString(2, txt_price.getText());
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
String addDate = dateFormat.format(txt_AddDate.getSelectedDate().getTime());
pst.setDate(3, java.sql.Date.valueOf(addDate));
pst.setInt(4, Integer.parseInt(txt_id.getText()));
pst.executeUpdate();
Show_Products_In_JTable();
JOptionPane.showMessageDialog(null, "Product Updated");
} catch (SQLException ex) {
Logger.getLogger(ProductInfo.class.getName()).log(Level.SEVERE, null, ex);
}
}
// update With Image
else{
try{
InputStream img = new FileInputStream(new File(imgpath));
String sql = "UPDATE ProductInfo SET Name = ?, Price = ?"
+ ", Date = ? WHERE ProductId = ?";
pst=conn.prepareStatement(sql);
pst.execute();
pst.setString(1, txt_name.getText());
pst.setString(2, txt_price.getText());
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
String addDate = dateFormat.format(txt_AddDate.getSelectedDate().getTime());
//pst.setString(3, addDate);
pst.setDate(3, java.sql.Date.valueOf(addDate));
pst.setBlob(4, img);
pst.setInt(5, Integer.parseInt(txt_id.getText()));
pst.executeUpdate();
Show_Products_In_JTable();
JOptionPane.showMessageDialog(null, "Product Updated");
}catch(Exception ex)
{
JOptionPane.showMessageDialog(null, ex.getMessage());
}
}
}else{
JOptionPane.showMessageDialog(null, "One Or More Fields Are Empty Or Wrong");
}
}
以下是变量声明
// Variables declaration - do not modify
private javax.swing.JTable JTable_Products;
private javax.swing.JButton btn_Image;
private javax.swing.JButton btn_delete;
private javax.swing.JButton btn_first;
private javax.swing.JButton btn_insert;
private javax.swing.JButton btn_last;
private javax.swing.JButton btn_next;
private javax.swing.JButton btn_previous;
private javax.swing.JButton btn_update;
private javax.swing.JPanel jPanel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JLabel lbl_date;
private javax.swing.JLabel lbl_id;
private javax.swing.JLabel lbl_image;
private javax.swing.JLabel lbl_img;
private javax.swing.JLabel lbl_name;
private javax.swing.JLabel lbl_price;
private datechooser.beans.DateChooserCombo txt_AddDate;
private javax.swing.JTextField txt_id;
private javax.swing.JTextField txt_name;
private javax.swing.JTextField txt_price;
// End of variables declaration
这是实体类，
public class Product {
private int id;
private String name;
private double price;
private String addDate;
private byte[] picture;
public Product(int pid, String pname, double pprice, String pAddDate, byte[] pimg)
{
this.id = pid;
this.name = pname;
this.price = pprice;
this.addDate = pAddDate;
this.picture = pimg;
}
public int getId()
{
return id;
}
public String getName()
{
return name;
}
public double getPrice()
{
return price;
}
public String getAddDate()
{
return addDate;
}
public byte[] getImage()
{
return picture;
}
我是初学者，不理解错误。有人请帮我解决一下吗？