JavaFX update a Sqlite table

I am currently working on a program the function of which is to store my passwords, and this is why I am using an SQL database called Users. This database contains tables for all the users which will be using the program. Those tables have four collumns: SiteName, Username, Password and AdditionalInfo. I am having a problem updating a specific row. This is my the code I get an error with:

public static void editPassword(String user, String siteEdited, String site, String usernamej, String password, String info){
     try{
         System.out.println(usernamej);
         Class.forName("org.sqlite.JDBC");
         c = DriverManager.getConnection("jdbc:sqlite:res/Users");
         c.setAutoCommit(false);
         stmt = c.createStatement();
         String update = "UPDATE " + user + " set Username = " + usernamej + " where SiteName = " + siteEdited;
         stmt.executeUpdate(update);
         stmt.close();
         c.close();
     }catch(Exception e){
         System.err.print( e.getClass().getName() + ": " + e.getMessage());
     }
 }

It is in a class made specifically for dealing with the sql database and it gets the following error when i try to change the username to 'test':

java.sql.SQLException: [SQLITE_ERROR] SQL error or missing database (no such column: test)