Updating database record in Java by using executeUpdate() function

Question

I'm trying to update record in mysql database using java. This is my code:

Statement stmt = con.createStatement();
String sql = "";
JOptionPane.showMessageDialog(null, "test");
sql = "update users set email='" + email1.getText() + "' WHERE fullname='" + user1 + "'";
stmt.executeUpdate(sql);
stmt.close();
con.close();

I'm getting this error: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: No operations allowed after statement closed.