public abstract class Database {

    public abstract Connection getConnection();
    public abstract void connect();
    public abstract void disconnect();
    public abstract boolean isConnected();

}

public class MySQL extends Database {

    private final String ip;
    private final int port;
    private final String database;
    private final String username;
    private final String password;

    public MySQL(String ip, int port, String database, String username, String password) {
        this.ip = ip;
        this.port = port;
        this.database = database;
        this.username = username;
        this.password = password;
    }

    private Connection connection;

    @Override
    public Connection getConnection() {
        return connection;
    }

    @Override
    public void connect() {
        if (isConnected()) {
            return;
        }

        try {
            connection = DriverManager.getConnection("jdbc:mysql://" + ip + ":" + port + "/" + database, username, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void disconnect() {
        if (isConnected()) {
            try {
                connection.close();
                connection = null;
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public boolean isConnected() {
        if(connection == null) {
            return false;
        }

        try {
            return connection.isClosed();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return false;
    }
}