public class App {

	private App(MysqlDB database) {
		this.database = database;
	}

	public final MysqlDB database;
	ExecutorService executor = Executors.newFixedThreadPool(5);

	BlockingQueue<String> taskQueue = new LinkedBlockingQueue<String>();

	static String username ="abc123"

        public static void main(String[] args) throws SQLException, Exception {

           Connection conn = DriverManager.getConnection(
			"jdbc:mysql://localhost/db",
			"user",
			"pass:35"
		);

		try {
			MysqlDB database = new MysqlDB(conn);
                         // do some stuff here, start threads, etc.
                }
		catch(Exception e){
			System.out.println(e);
		}
       }

----------------------------------------------------------
class workerThread implements Runnable{

public void run() {
   System.out.println(username);  // 'cannot resolve symbol'

   String query = 'select * from foobar";
   database.doQuery(query);  // doQuery is defined in a separate class file.  It WORKS in the main App, but fails here with 'cannot resolve symbol"
}
}