Java SQL，一般错误org.hsqldb.HsqlException

try {
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:file:mydb;shutdown=true");
    Statement stmt = conn.createStatement();
    String sql = "SELECT * FROM non_existent_table"; // 错误的表名
    ResultSet rs = stmt.executeQuery(sql);
} catch (SQLException e) {
    e.printStackTrace();
}

try {
    Class.forName("org.hsqldb.jdbc.JDBCDriver");
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:file:mydb;shutdown=true");
} catch (ClassNotFoundException | SQLException e) {
    e.printStackTrace();
}

try {
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:file:mydb;shutdown=true");
    conn.setAutoCommit(false);
    Statement stmt = conn.createStatement();
    String sql = "UPDATE users SET balance = balance - 100 WHERE id = 1";
    stmt.executeUpdate(sql);
    conn.commit();
} catch (SQLException e) {
    if (conn != null) {
        try {
            conn.rollback();
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
    }
    e.printStackTrace();
} finally {
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
    }
}