对Base而不是DB使用Try-with-resources

public class Base implements AutoCloseable {
    private Connection connection;

    public Base(String url, String user, String password) throws SQLException {
        this.connection = DriverManager.getConnection(url, user, password);
    }

    public ResultSet executeQuery(String sql) throws SQLException {
        Statement stmt = connection.createStatement();
        return stmt.executeQuery(sql);
    }

    @Override
    public void close() throws Exception {
        if (connection != null) {
            connection.close();
        }
    }
}

public static void main(String[] args) {
    String url = "jdbc:mysql://localhost:3306/mydatabase";
    String user = "username";
    String password = "password";

    try (Base base = new Base(url, user, password)) {
        ResultSet rs = base.executeQuery("SELECT * FROM mytable");
        while (rs.next()) {
            // 处理结果集
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}