package singleton;

/**
 * Thread-safe Singleton using double-checked locking.
 */
public class DatabaseConnection {
    private static volatile DatabaseConnection instance;
    private final String url;
    private int queryCount = 0;

    private DatabaseConnection() {
        this.url = "jdbc:mysql://localhost:3306/myapp";
        System.out.println("Establishing connection to " + url);
    }

    public static DatabaseConnection getInstance() {
        if (instance == null) {
            synchronized (DatabaseConnection.class) {
                if (instance == null) {
                    instance = new DatabaseConnection();
                }
            }
        }
        return instance;
    }

    public String executeQuery(String sql) {
        queryCount++;
        return "Result #" + queryCount + " for: " + sql;
    }

    public int getQueryCount() { return queryCount; }
    public String getUrl()     { return url; }
}