title: void cannot be dereferenced
body: <p>I have a method of editing members, and I want to print out errors into a file, but I keep getting the void cannot be dereferenced error if I try to print out the stack trace into a Error_Report.txt file. Is there anyway I can print it out?
  This is my code.</p>
  
  <pre><code>public void edit() {
    FileWriter fw = new FileWriter(new File("Error_Report.txt"));
    Connection con;
    Statement stmt;
    ResultSet rs;
  
    int id = (int)_id.getSelectedItem();
    String name = _name.getText();
    String user = _username.getText();
    String pass = _password.getText();
    String pos = _position.getSelectedItem().toString();
  
    try {
      Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
      con = DriverManager.getConnection("jdbc:odbc:collegesys", 
                                        "root", "0blivi0n");
  
      stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                                 ResultSet.CONCUR_READ_ONLY);
  
      PreparedStatement prep = con.prepareStatement("UPDATE `main` WHERE ID = ?");
      prep.setInt(1, id);
      prep.setString(2, name);
      prep.setString(3, user);
      prep.setString(4, pass);
      prep.setString(5, pos);
  
      prep.execute();
    } catch(SQLException sqle) {
      String sql = sqle.printStackTrace().toString();
      fw.write("" + sql);
    } catch(ClassNotFoundException cnfe) {
      fw.write("" + cnfe);
    }
  }
  </code></pre>