从 Oracle DB 加载 Java JTable 数据

Question

我在将从“listallButton”检索到的数据正确显示到 JTable 中时遇到问题。数据库正在将SELECT * FROM ATM信息作为一组字符串正确发送。我不确定它是否被正确接收和记录，因为 JTables 没有显示任何数据并且出现空指针异常:

    import java.awt.*;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.io.ObjectInputStream;
    import java.io.ObjectOutputStream;
    import java.net.Socket;
    import javax.swing.*;
    import javax.swing.border.Border;
    import javax.swing.table.*;
    import java.util.*;
    import javax.swing.table.AbstractTableModel;

    public class AtmView extends JApplet implements ActionListener{
        final static String banner = "WELCOME TO SHETH BANK!";
        JLabel bannerLabel;
        Border blackline;

        CardLayout myLayout;
        JPanel screensPanel; //main center panel

        JPanel loginPanel; //login panel
        JButton loginButton; //login button
        JTextField accountNumber; //login account number field
        JPasswordField password; //login password/PIN field
        String access_lvl; //login access level
        public String account;
        String pass;
        DataObject communicationObject;
        final static String LOGIN = "LOGIN";

        JPanel empPanel; //employee panel
        CardLayout empLayout; //employee center panel
        JButton createacctButton; //employee create account button
        JButton listallButton; //employee list all accounts button
        JPanel empcenterPanel;
        final static String EMP1 = "EMPLOYEE";
        String balance;
        String withdrawal_amount;
        String withdraw_amount;
        JLabel balanceDisplay;

  final static String LIST = "listallPanel";
  JPanel listallPanel;
  JTable table;
  String[] data;
  String[][] data2;
  String[] temp;
  String row;
  DefaultTableModel tbm; 
  JLabel listdisplay;
  String acclist;
  ArrayList<String> al;

  JButton empBackButton; //emp back
  JButton emplogoutButton; //emp logout
  JButton empwithdrawButton;

  JPanel custPanel; //customer panel
  final static String CUST = "CUSTOMER";

  JButton checkbalButton; //check balance
  JButton withdrawButton; //withdraw
  JButton depositButton; //deposit
  JButton transferButton; //transfer




  JLabel display; //server response display area


    @Override
  public void init(){

    getContentPane().setVisible(true);
    getContentPane().setLayout(new BorderLayout());
    getContentPane().setBackground(Color.BLUE);
    //getContentPane().setBorder(blackline);
    bannerLabel = new JLabel(banner,JLabel.CENTER);
    bannerLabel.setVerticalTextPosition(JLabel.CENTER);
    bannerLabel.setHorizontalTextPosition(JLabel.CENTER);
    bannerLabel.setFont(new Font("Serif", Font.BOLD, 26));
    bannerLabel.setForeground(Color.yellow);
    blackline = BorderFactory.createLineBorder(Color.black);

    //bannerLabel.setBorder(blackline);
    add(bannerLabel, BorderLayout.NORTH);
    //bannerLabel.setBorder(BorderFactory.createMatteBorder(0, 0, 2, 0, Color.BLACK));

    myLayout = new CardLayout();
    screensPanel = new JPanel();
    screensPanel.setLayout(myLayout);
    add(screensPanel, BorderLayout.CENTER);

    //================ LOGIN VIEW ================================== 

    loginPanel = new JPanel(new GridLayout(3,1));
    loginPanel.setBackground(Color.BLUE);
    JLabel loginTitle = new JLabel("ENTER LOGIN INFO", JLabel.CENTER);
    //loginTitle.setVerticalAlignment(SwingConstants.TOP);
    loginTitle.setFont(new Font("Serif", Font.BOLD, 20));
    loginTitle.setForeground(Color.yellow);
    loginPanel.add(loginTitle);

    JPanel accountInfo = new JPanel(new GridLayout(2,1));
    accountInfo.setBackground(Color.blue);
    JPanel accNum = new JPanel();
    accNum.setBackground(Color.BLUE);
    JLabel accLabel = new JLabel("Account Number: ", JLabel.CENTER);
    accLabel.setFont(new Font("Serif", Font.BOLD, 14));
    accLabel.setForeground(Color.yellow);
    accountNumber = new JTextField(4);
    accountNumber.setHorizontalAlignment(JTextField.CENTER);
    accNum.add(accLabel);
    accLabel.setLabelFor(accountNumber);
    accNum.add(accountNumber); 
    accountInfo.add(accNum);
    JPanel pw = new JPanel();
    pw.setBackground(Color.BLUE);
    JLabel pwLabel = new JLabel("Password/PIN: ", JLabel.CENTER);
    pwLabel.setFont(new Font("Serif", Font.BOLD, 14));
    pwLabel.setForeground(Color.yellow);
    password = new JPasswordField(4);
    password.setHorizontalAlignment(JTextField.CENTER);
    pw.add(pwLabel);
    pwLabel.setLabelFor(password);
    pw.add(password);
    accountInfo.add(pw);
    loginPanel.add(accountInfo);

    JPanel logBut = new JPanel();
    loginButton = new JButton("Login");
    loginButton.addActionListener(this);
    logBut.setBackground(Color.blue);
    logBut.add(loginButton);

    loginPanel.add(logBut);

    screensPanel.add(loginPanel, "LOGIN");

    //================ EMPLOYEE VIEW ==================================

    empPanel = new JPanel(new BorderLayout());
    empPanel.setBackground(Color.BLUE);
    JLabel empLabel = new JLabel("Employee View",JLabel.CENTER);
    empLabel.setVerticalTextPosition(JLabel.CENTER);
    empLabel.setHorizontalTextPosition(JLabel.CENTER);
    empLabel.setFont(new Font("Serif", Font.BOLD, 20));
    empLabel.setForeground(Color.yellow);
    empPanel.add(empLabel, BorderLayout.NORTH);

    empLayout = new CardLayout();
    empcenterPanel = new JPanel();
    empcenterPanel.setBackground(Color.blue);
    empcenterPanel.setLayout(empLayout);
    empPanel.add(empcenterPanel, BorderLayout.CENTER);

    JPanel empbuttonPanel = new JPanel(new GridLayout(3,2));
    empbuttonPanel.setBackground(Color.blue);
    checkbalButton = new JButton("Check Balance"); 
    checkbalButton.addActionListener(this);
    empbuttonPanel.add(checkbalButton);
    withdrawButton = new JButton("Withdraw"); 
    withdrawButton.addActionListener(this);
    empbuttonPanel.add(withdrawButton);
    depositButton = new JButton("Deposit"); 
    depositButton.addActionListener(this);
    empbuttonPanel.add(depositButton);
    transferButton = new JButton("Transfer");
    transferButton.addActionListener(this);
    empbuttonPanel.add(transferButton);
    createacctButton = new JButton("Create account");
    createacctButton.addActionListener(this);
    empbuttonPanel.add(createacctButton);
    listallButton = new JButton("List all accounts");
    listallButton.addActionListener(this);
    empbuttonPanel.add(listallButton);
    empcenterPanel.add(empbuttonPanel, "EmpButtonPanel");


    createPanel = new JPanel(new GridLayout(6,1));
    createPanel.setBackground(Color.blue);
    JLabel createTitle = new JLabel("Enter new account info: ",JLabel.CENTER);
    createTitle.setVerticalTextPosition(JLabel.CENTER);
    createTitle.setHorizontalTextPosition(JLabel.CENTER);
    createTitle.setFont(new Font("Serif", Font.BOLD, 18));
    createTitle.setForeground(Color.yellow);
    createPanel.add(createTitle);

    JPanel cloginPanel = new JPanel(new FlowLayout());
    cloginPanel.setBackground(Color.blue);
    JLabel cloginLabel = new JLabel("Account number: ",JLabel.CENTER);
    cloginLabel.setVerticalTextPosition(JLabel.CENTER);
    cloginLabel.setHorizontalTextPosition(JLabel.CENTER);
    cloginLabel.setFont(new Font("Serif", Font.BOLD, 14));
    cloginLabel.setForeground(Color.yellow);
    cloginPanel.add(cloginLabel);
    createloginField = new JTextField(4);
    createloginField.setHorizontalAlignment(JTextField.CENTER);
    cloginLabel.setLabelFor(createloginField);
    cloginPanel.add(createloginField);
    createPanel.add(cloginPanel);
    JPanel cpinPanel = new JPanel(new FlowLayout());
    cpinPanel.setBackground(Color.blue);
    JLabel cpinLabel = new JLabel("PIN: ",JLabel.CENTER);
    cpinLabel.setVerticalTextPosition(JLabel.CENTER);
    cpinLabel.setHorizontalTextPosition(JLabel.CENTER);
    cpinLabel.setFont(new Font("Serif", Font.BOLD, 14));
    cpinLabel.setForeground(Color.yellow);
    cpinPanel.add(cpinLabel);
    createpinField = new JTextField(4);
    createpinField.setHorizontalAlignment(JTextField.CENTER);
    cloginLabel.setLabelFor(createpinField);
    cpinPanel.add(createpinField);
    createPanel.add(cpinPanel);
    JPanel cbalPanel = new JPanel(new FlowLayout());
    cbalPanel.setBackground(Color.blue);
    JLabel cbalLabel = new JLabel("Starting balance: ",JLabel.CENTER);
    cbalLabel.setVerticalTextPosition(JLabel.CENTER);
    cbalLabel.setHorizontalTextPosition(JLabel.CENTER);
    cbalLabel.setFont(new Font("Serif", Font.BOLD, 14));
    cbalLabel.setForeground(Color.yellow);
    cbalPanel.add(cbalLabel);
    createbalanceField = new JTextField(10);
    createbalanceField.setHorizontalAlignment(JTextField.CENTER);
    cbalLabel.setLabelFor(createbalanceField);
    cbalPanel.add(createbalanceField);
    createPanel.add(cbalPanel);
    JPanel clvlPanel = new JPanel(new FlowLayout());
    clvlPanel.setBackground(Color.blue);
    JLabel clvlLabel = new JLabel("Access level (1 for Employee, 2 for Customer): ",JLabel.CENTER);
    clvlLabel.setVerticalTextPosition(JLabel.CENTER);
    clvlLabel.setHorizontalTextPosition(JLabel.CENTER);
    clvlLabel.setFont(new Font("Serif", Font.BOLD, 14));
    clvlLabel.setForeground(Color.yellow);
    clvlPanel.add(clvlLabel);
    createlvlField = new JTextField(1);
    createlvlField.setHorizontalAlignment(JTextField.CENTER);
    cbalLabel.setLabelFor(createlvlField);
    clvlPanel.add(createlvlField);
    createPanel.add(clvlPanel);
    JPanel createbutPanel = new JPanel();
    createbutPanel.setBackground(Color.blue);
    createButton = new JButton("Create");
    createButton.addActionListener(this);
    createbutPanel.add(createButton);
    createPanel.add(createbutPanel);
    empcenterPanel.add(createPanel, "createPanel");

    listallPanel = new JPanel(new BorderLayout());
    listallPanel.setBackground(Color.blue);
    JLabel listTitle = new JLabel("All accounts in system: ",JLabel.CENTER);
    listTitle.setVerticalTextPosition(JLabel.CENTER);
    listTitle.setHorizontalTextPosition(JLabel.CENTER);
    listTitle.setFont(new Font("Serif", Font.BOLD, 16));
    listTitle.setForeground(Color.yellow);
    listallPanel.add(listTitle,BorderLayout.NORTH);

    String[] columnNames = {"Account Number","PIN","Access Level","Balance",};
    String [][] rowTest = {{"1111","1111","1","1000",},{"1111","1111","1","1000",}};
    String delimiter = ",";

    tbm = new DefaultTableModel();  
    tbm.addColumn("Account Number"); 
    tbm.addColumn("PIN"); 
    tbm.addColumn("Access Level"); 
    tbm.addColumn("Balance");

    table = new JTable(tbm);
    JScrollPane scrollPane = new JScrollPane(table);
    listallPanel.add(scrollPane,BorderLayout.CENTER);        

    empcenterPanel.add(listallPanel, "listallPanel");


    JPanel logoutPanel = new JPanel(new FlowLayout());
    emplogoutButton = new JButton("Logout");
    emplogoutButton.addActionListener(this);
    empBackButton = new JButton("Back");
    empBackButton.addActionListener(this);
    logoutPanel.setBackground(Color.blue);
    logoutPanel.add(emplogoutButton);
    logoutPanel.add(empBackButton);
    empPanel.add(logoutPanel, BorderLayout.SOUTH);

    screensPanel.add(empPanel, "EMPLOYEE");

    //================ CUSTOMER VIEW ==================================


    }



  public void actionPerformed(ActionEvent event) {
      if (event.getSource() == loginButton) {
          account = accountNumber.getText();
          pass = password.getText();
          String query = "SELECT access_level FROM ATM a WHERE a.account_number='"+account+"' AND a.pin='"+pass+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              access_lvl = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
          if ((access_lvl.charAt(0)) == '1') {
              myLayout.show(screensPanel, EMP1);
              empLayout.first(empcenterPanel);}
          else {myLayout.show(screensPanel, CUST); } }

      else if(event.getSource() == emplogoutButton) {
          accountNumber.setText("");
          password.setText("");
          account = "";
          pass = "";
          empLayout.first(empcenterPanel);
          myLayout.show(screensPanel, LOGIN);
          doLayout();}

      else if(event.getSource() == checkbalButton) {

      String query = "SELECT balance FROM ATM a WHERE a.account_number='"+account+"' AND a.pin='"+pass+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
          balanceDisplay.setText(balance);
          //balanceDisplayPanel.add(balanceDisplay);
          //checkBalancePanel.add(balanceDisplayPanel);
          empLayout.show(empcenterPanel, EMPBAL); }

      else if(event.getSource() == empBackButton) {
          empLayout.first(empcenterPanel); }

      else if(event.getSource() == withdrawButton) {
          empLayout.show(empcenterPanel, EMPWITH); }  

      else if(event.getSource() == empwithdrawButton) {
      withdraw_amount = withdrawField.getText();
      Integer w_amt = Integer.valueOf(withdraw_amount);
      String query = "SELECT balance FROM ATM a WHERE a.account_number='"+account+"' AND a.pin='"+pass+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
          Integer oldbalance = Integer.valueOf(balance);
          Integer newbalanceamount = oldbalance - w_amt;
          balance2 = "" + newbalanceamount;
          String query2 = "UPDATE ATM SET balance='"+balance2+"' WHERE account_number='"+account+"' AND pin='"+pass+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query2);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              //balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e); }
      withdrawField.setText("");
      empLayout.first(empcenterPanel); }

      else if(event.getSource() == depositButton) {
         empLayout.show(empcenterPanel, EMPDEP); }

      else if(event.getSource() == empdepositButton) {
      deposit_amount = depositField.getText();
      Integer d_amt = Integer.valueOf(deposit_amount);
      String query = "SELECT balance FROM ATM a WHERE a.account_number='"+account+"' AND a.pin='"+pass+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
          Integer oldbalance2 = Integer.valueOf(balance);
          Integer newbalanceamount2 = oldbalance2 + d_amt;
          balance3 = "" + newbalanceamount2;
          String query2 = "UPDATE ATM SET balance='"+balance3+"' WHERE account_number='"+account+"' AND pin='"+pass+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query2);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              //balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
          depositField.setText("");
          empLayout.first(empcenterPanel); }

      else if(event.getSource() == transferButton) {
         empLayout.show(empcenterPanel, EMPTNS); }

      else if(event.getSource() == transferamountButton) {
      fromAccount = fromField.getText();
      toAccount = toField.getText();
      transAmount = transferAmount.getText();
      Integer t_amt = Integer.valueOf(transAmount);
      String query = "SELECT balance FROM ATM a WHERE a.account_number='"+fromAccount+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
      Integer fromBalance = Integer.valueOf(balance);
      String query2 = "SELECT balance FROM ATM a WHERE a.account_number='"+toAccount+"'";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query2);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
      Integer toBalance = Integer.valueOf(balance);
      Integer newFromBalance = fromBalance - t_amt;
      Integer newToBalance = toBalance + t_amt;
      String newFBalance = "" + newFromBalance;
      String newTBalance = "" + newToBalance;
      String query3 = "UPDATE ATM SET balance='"+newFBalance+"' WHERE account_number='"+fromAccount+"'";
      try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query3);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              //balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
      String query4 = "UPDATE ATM SET balance='"+newTBalance+"' WHERE account_number='"+toAccount+"'";    
      try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query4);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              //balance = communicationObject.getMessage();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}      
      toField.setText("");
      fromField.setText("");
      transferAmount.setText("");
      empLayout.first(empcenterPanel); }     

      else if(event.getSource() == createacctButton) {
         empLayout.show(empcenterPanel, CREATE); }

      else if(event.getSource() == createButton) {
          createLogin = createloginField.getText();
          createPin = createpinField.getText();
          createLvl = createlvlField.getText();
          createBalance = createbalanceField.getText();
          String query = "INSERT INTO ATM VALUES ("+createLogin+","+createPin+","+createLvl+","+createBalance+")";
          try {
              communicationObject = new DataObject();
              communicationObject.setMessage(query);
              Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
              ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
              ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
              myOutputStream.writeObject(communicationObject);
              communicationObject = (DataObject)myInputStream.readObject();
              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }   
          catch(Exception e){System.out.println(e);}
          createloginField.setText("");
          createpinField.setText("");
          createlvlField.setText("");
          createbalanceField.setText("");
          empLayout.first(empcenterPanel); }

        else if(event.getSource() == listallButton) {
          String query = "SELECT * FROM ATM";
          String delimiter = ",";
          String input = "go";
          int count=0;
          al = new ArrayList<String>();

              try {
                  communicationObject = new DataObject();
                  communicationObject.setMessage(query);
                  Socket socketToServer = new Socket("sunlab32.njit.edu",31414);
                  ObjectOutputStream myOutputStream = new ObjectOutputStream(socketToServer.getOutputStream());
                  ObjectInputStream myInputStream = new ObjectInputStream(socketToServer.getInputStream());
                  myOutputStream.writeObject(communicationObject);
                  communicationObject = (DataObject)myInputStream.readObject();
                  input = communicationObject.getMessage();
                  if (input != "stop") {
                      al.add(input);
                      data[count] = input;
                      count++; }

                  for (int i=0;i<data.length;i++) {
                      row = data[i];
                      temp = row.split(delimiter);
                      tbm.addRow(new String[] {temp[0],temp[1],temp[2],temp[3]}); } 

                  table.setModel(tbm);
                  table.repaint();




              //Object Object_Array[]=al.toArray();
              //data=new String[Object_Array.length];
              //for (int i=0;i<data.length;i++) {data[i]=Object_Array[i].toString();}


              myOutputStream.close();
              myInputStream.close();
              socketToServer.close(); }
              catch(Exception e){System.out.println(e);}   

          empLayout.show(empcenterPanel, LIST);  }



        }   }  

堆栈跟踪:

java.lang.NullPointerException at AtmView.actionPerformed(AtmView.java:757) at 
javax.swing.AbstractButton.fireActionPerformed(Unknown Source) at 
javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source) at 
javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source) at 
javax.swing.DefaultButtonModel.setPressed(Unknown Source) at 
javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source) at 
java.awt.Component.processMouseEvent(Unknown Source) at 
javax.swing.JComponent.processMouseEvent(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 

Answer 1

空点异常可能是由数据库中的某些空列引起的。你的做法不好，如果数据库中有大量记录的话会让你的程序崩溃，更好的方法是使用分页来避免加载大量记录。