How can i load data from text file to Jlist in java swing?

Question

I'm learning java. I have trouble when I click JButton to load data from text file to JList, but it notices error "java.lang.NumberFormatException: For input string: """. First of all, I input data from 4 JTextField to JList then save file text. My txt file has content: 1-java-3-4. Someone help me, please. Thank. Here is my code button save and load data:

private void btAddBookActionPerformed(java.awt.event.ActionEvent evt) {  
String BookId = txtBookID.getText();
            String BookName = txtBookName.getText();
            String Quantity = txtQuantity.getText();
            String Price = txtPrice.getText();
            if(BookId.equals("")|| BookId.equalsIgnoreCase("Type Here") || BookName.equals("")|| BookName.equalsIgnoreCase("Type Here") || Quantity.equals("")|| Quantity.equalsIgnoreCase("Type Here")||Price.equals("")|| Price.equalsIgnoreCase("Type Here")){
                txtBookID.setText("Type Here");
                txtBookName.setText("Type Here");
                txtPrice.setText("Type Here");
                txtQuantity.setText("Type Here");
            }else{
                listmodel.addElement(BookId+"-"+BookName+"-"+Quantity+"-
"+Price);
                booklist.setModel(listmodel);
                txtBookID.setText("");
                txtBookName.setText("");
                txtQuantity.setText("");
                txtPrice.setText("");         
            }

private void btLoadDBActionPerformed(java.awt.event.ActionEvent evt) {                                         
    BufferedReader br = null;
    try{
        br = new BufferedReader(new FileReader("BookList.txt"));
        int val = Integer.parseInt(br.readLine());
        for (int i = 0; i < val; i++) {
            String ss = br.readLine();
            listmodel.addElement(ss);
        }
        booklist.setModel(listmodel);
    }
    catch(Exception e){
        System.out.println(""+e);
    }
    finally{
        try{
            br.close();
        }
        catch(Exception e){
            System.out.println(""+e);
        }
    }
}     

Answer 1

Looking closer at your code, it seems that you don't need the integer-parsing at all. The problem is that you're reading the file the wrong way. Instead of a for loop, a common idiom for reading a text file line-by-line (when you don't know the exact size of the file) is with a while loop as follows:

br = new BufferedReader(new FileReader("BookList.txt"));
String line;
while ((line = br.readLine()) != null) {
    listmodel.addElement(line);
}
booklist.setModel(listmodel);