public void addBook() {
    list.add(new Book(JOptionPane.showInputDialog("Enter name"),
    JOptionPane.showInputDialog("Enter Author"),
    Integer.parseInt(JOptionPane.showInputDialog("Enter price"))
    ));
  }

  public void showBooks() {
    String st=" ";
    for (Book x:list){
        st += ""+x+"/n";
    }
    JOptionPane.showMessageDialog(st);

    }