我迫切需要一些帮助。我正在做一个 StockManagement 项目。由于错误，我无法将项目插入到数据库中：
org.bil.service.StockManagerImpl.actionPerformed 的线程“AWT-EventQueue-0”java.lang.NullPointerException 中的异常（StockManagerImpl.java:163）
我无法解决它。我的代码很长，但我认为这将帮助您找到问题所在。
public class StockManagerImpl implements ActionListener
{
Date entryDate;
int itemNo;
String itemName;
double unitPrice;
double qty;
double totalPrice;
String supplier;
String remarks;
JTextField txtEntryDate;
JTextField txtItemNo;
JTextField txtItemName;
JTextField txtUnitPrice;
JTextField txtQty;
JTextField txtTotalPrice;
JTextField txtSupplier;
JTextField txtRemarks;
JButton BttnSaveAdded;
StockManagerDAO stockManagerDAO;
Toolkit kit = Toolkit.getDefaultToolkit();
Dimension screenSize = kit.getScreenSize();
int screenHeight = screenSize.height;
int screenWidth = screenSize.width;
Image img = kit.getImage("images/icon.JPG");
JFrame newFrame;
public void addNewItem() {
newFrame = new JFrame("Add New");
newFrame.setSize(220, 250);
newFrame.setResizable(false);
newFrame.setIconImage(img);
JLabel lblEntryDate = new JLabel("Item EntryDate: ");
JLabel lblItemNo = new JLabel("Item No: ");
JLabel lblItemName = new JLabel("Item Name: ");
JLabel lblUnitPrice = new JLabel("Item UnitPrice: ");
JLabel lblQty = new JLabel("Item Qty: ");
JLabel lblTotalPrice = new JLabel("Item TotalPrice: ");
JLabel lblSupplier = new JLabel("SupplierDetails: ");
JLabel lblRemarks = new JLabel("Remarks: ");
JLabel lblEmpty1 = new JLabel("");
JLabel lblEmpty2 = new JLabel("");
//txtEntryDate = new JTextField(10);
// JFormattedTextField txtEntryDate = new JFormattedTextField(new SimpleDateFormat("d-M-yyyy"));
// txtEntryDate.setValue(new Date());
txtEntryDate = new JFormattedTextField(new SimpleDateFormat("d-M-yyyy"));
txtItemNo = new JTextField(10);
txtItemName = new JTextField(10);
txtUnitPrice = new JTextField(10);
txtQty = new JTextField(10);
txtTotalPrice = new JTextField(10);
txtSupplier = new JTextField(10);
txtRemarks = new JTextField(10);
JButton bttnAdd = new JButton("Save");
JButton bttnCancel = new JButton("Cancel");
bttnAdd.addActionListener(this);
bttnCancel.addActionListener(this);
JPanel centerPane = new JPanel();
JPanel bottomPane = new JPanel();
centerPane.add(lblEntryDate);
centerPane.add(txtEntryDate);
centerPane.add(lblItemNo);
centerPane.add(txtItemNo);
centerPane.add(lblItemName);
centerPane.add(txtItemName);
centerPane.add(lblUnitPrice);
centerPane.add(txtUnitPrice);
centerPane.add(lblQty);
centerPane.add(txtQty);
centerPane.add(lblTotalPrice);
centerPane.add(txtTotalPrice);
centerPane.add(lblSupplier);
centerPane.add(txtSupplier);
centerPane.add(lblRemarks);
centerPane.add(txtRemarks);
bottomPane.add(bttnAdd);
bottomPane.add(bttnCancel);
centerPane.setLayout(new GridLayout(0, 2));
newFrame.getContentPane().add(centerPane, BorderLayout.CENTER);
newFrame.getContentPane().add(bottomPane, BorderLayout.SOUTH);
newFrame.setLocation(screenWidth / 4, screenHeight / 4);
newFrame.show();
System.out.println("Show AddItem Window");
}
@Override
public void actionPerformed(ActionEvent e) {
if(e.getActionCommand()=="Save")
{
System.out.println("Enterered ActionListener for AddItem");
entryDate = (Date)((JFormattedTextField) txtEntryDate).getValue();
if(txtItemNo.equals(""))
{
itemNo = 0;
}
try
{
itemNo = Integer.parseInt(txtItemNo.getText());
unitPrice = Double.parseDouble(txtUnitPrice.getText());
qty = Double.parseDouble(txtQty.getText());
}
catch(NumberFormatException ne)
{
System.out.println("Integer .ParseInt error" + ne);
}
itemName = txtItemName.getText();
totalPrice = unitPrice * qty;
supplier = txtSupplier.getText();
remarks = txtRemarks.getText();
if (txtItemName.equals(""))
{
JOptionPane.showMessageDialog(null, "Please enter Item name.");
}
if (txtUnitPrice.getText() == "") {
JOptionPane.showMessageDialog(null,
"Please enter UnitPrice for the item");
}
if (txtQty.getText() == "") {
JOptionPane.showMessageDialog(null,
"Please enter Quantity of item to be added");
} else {
Items item = new Items(entryDate, itemNo, itemName, unitPrice, qty,
totalPrice, supplier, remarks);
stockManagerDAO.addNewItem(item);
JOptionPane.showMessageDialog(null, "Item Saved");
}
if(e.getActionCommand()=="Cancel")
{
newFrame.setVisible(false);
}
}
}
}
Items.java
public class Items
{
Date entryDate;
int itemNo;
String itemName;
double unitPrice;
double qty;
double totalPrice;
String supplier;
String remarks;
// default constructor
public Items()
{
entryDate = new Date() ;
itemNo = 0;
itemName="";
unitPrice=0;
qty=0;
totalPrice=0;
supplier="";
remarks="";
}
public Items(Date entryDate,int itemNo,String itemName,double unitPrice,double qty,double totalPrice,String supplier,String remarks)
{
this.entryDate = entryDate;
this.itemNo = itemNo;
this.itemName = itemName;
this.unitPrice = unitPrice;
this.qty =qty;
this.totalPrice=totalPrice;
this.supplier=supplier;
this.remarks=remarks;
}
//getter and setter methods
}
希望这两个类足以解决问题。请帮帮我。谢谢