尝试从二进制顺序访问文件读取时为NullPointer

Question

就像问题中所说的那样，我正在尝试编写一个程序，该程序将接收输入的信息并将该信息转换为二进制顺序访问文件。据我所知，该部分工作正常（没有异常，文件存在写入的内容，但是我无法分辨）。我也可以很好地打开二进制文件，但是当我尝试从中读取二进制文件时，每次都会得到NullPointerException，但是我知道一个事实，即该文件至少具有 something 。

我们将不胜感激！谢谢。

此方法打开二进制文件以供输出

    private int OpenFileOut() {
          jfc.setFileSelectionMode(JFileChooser.FILES_ONLY);
          int result = jfc.showOpenDialog(this);
          if (result == jfc.CANCEL_OPTION) {
             return 1;
          }
          file = jfc.getSelectedFile();

           try {
              fon = new FileOutputStream(file);
              out = new DataOutputStream(fon);        
           }                                        
           catch ( IOException ioe ) {
              JOptionPane.showMessageDialog( this, ioe.toString(), "Error",  
               JOptionPane.ERROR_MESSAGE );
              System.exit( 1 );        
           }
           JOptionPane.showMessageDialog(null, "Successfully Opened");
           return 0; 

           }

这下一部分将写入二进制文件

    private void AddToFile() {
       String name = "";
       String id = "";
       String qu = "";
       String numin = "";
       String bp = "";
       for (int x = 0; x < tools.getNumberOfToolItems(); x++) {
          name = name + tools.toolArray[x].getName() + " ";
          id = id  + tools.toolArray[x].getID() + " ";
          qu = qu  + tools.toolArray[x].getQuality() + " ";
          numin = numin + tools.toolArray[x].getNumberInStock() + " ";
          bp = bp + tools.toolArray[x].getPrice() + " ";
       }
       StringTokenizer names = new StringTokenizer(name," ");
       StringTokenizer ids = new StringTokenizer(id," ");
       StringTokenizer qus = new StringTokenizer(qu," ");
       StringTokenizer numins = new StringTokenizer(numin," ");
       StringTokenizer bps = new StringTokenizer(bp," ");

       String nhold;
       int idhold;
       int quahold;
       int numinhold;
       double bphold;
       for(int x = 0; x < tools.getNumberOfToolItems(); x++) {
          try {
             nhold = names.nextToken();
             System.out.println(nhold);
             out.writeUTF(nhold);
             idhold = Integer.parseInt(ids.nextToken());
             out.writeInt(idhold);
             quahold = Integer.parseInt(qus.nextToken());
             out.writeInt(quahold);
             numinhold = Integer.parseInt(numins.nextToken());
             out.writeInt(numinhold);
             bphold = Double.parseDouble(bps.nextToken());
             out.writeDouble(bphold);
          }
          catch (IOException ioe) {
             JOptionPane.showMessageDialog(null, ioe.toString(), "Error", 
              JOptionPane.ERROR_MESSAGE);
             System.exit( 1 );
          }
          }
          try {
             out.close();
          }
          catch (IOException ioe) {
             JOptionPane.showMessageDialog(null, ioe.toString(), "Error", 
              JOptionPane.ERROR_MESSAGE);
             System.exit( 1 );
          } 
    }

下一部分将打开INput的二进制文件

    private void OpenFileIn() {
       jfc.setFileSelectionMode(JFileChooser.FILES_ONLY);
       int result = jfc.showOpenDialog(this);
       if (result == jfc.CANCEL_OPTION) {
          return;
       }
       file = jfc.getSelectedFile();
       try {
          FileInputStream fin = new FileInputStream(file);
          BufferedInputStream bin = new BufferedInputStream(fin);
          in = new DataInputStream(bin);
       }
       catch (FileNotFoundException fnf) {
           System.exit(1);
       }
       JOptionPane.showMessageDialog(null,"Successfully Opened");



    }

最后，最后一部分是给我的问题，它应该从二进制文件中读取。在第一个“读取”中，它抛出NPException

    public void Populate() {
       int x = 2;
       try {
          while (true) {
             String nme = in.readUTF();
             int ida = in.readInt();
             int quali = in.readInt();
             int nums = in.readInt();
             double pb = in.readDouble(); 
             tools.insert(nme,ida,quali,nums,pb);
             x++;
             System.out.println(x);
          }
       }
       catch (EOFException eof) {
          JOptionPane.showMessageDialog(null,"File successfully read");
       }
       catch (IOException ioe) {
          JOptionPane.showMessageDialog( this, ioe.toString(), "Error",  
           JOptionPane.ERROR_MESSAGE );
          System.exit( 1 );
       }
       try {
          in.close();

       }
       catch (IOException ioe) {
          JOptionPane.showMessageDialog( this, ioe.toString(), "Error",  
            JOptionPane.ERROR_MESSAGE );
          System.exit( 1 );
       }
     }

如果有人可以帮助我阅读本书，我会亲吻他们，因为我花了很长时间盯着这个屏幕。

编辑：

根据要求，以下是我称为“填充”和“ OpenFile”的代码：

    if (eve.getSource() == popFile) {
                Populate();
       }

          if (eve.getSource() == openBin) {
             OpenBSAFile();
          }

    public void OpenBSAFile() {
       OpenFileOut();
    }