PreparedStatement不能动态设置表名和列名

static String url = "jdbc:mysql://localhost:3306/test?characterEncoding=utf8&useSSL=true";
	static String user = "root";
	static String password = "root";
	public static void main(String[] str) throws SQLException {
		Driver driver = new com.mysql.jdbc.Driver();
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		// set property
		Properties props = new Properties();
		props.setProperty("user", user);
		props.setProperty("password", password);
		try {
			// 连接数据库
			connection = driver.connect(url, props);
			// 使用占位符的SQl语句
			String sql = "insert into ?(id,username,age)" + "values(?,?,?)";
			preparedStatement = connection.prepareStatement(sql);
			preparedStatement.setString(1, "member5");
			preparedStatement.setInt(2, 6);
			preparedStatement.setString(3, "tom");
			preparedStatement.setInt(4, 29);
			// 执行更新操作
			preparedStatement.executeUpdate();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			// 释放资源
			connection.close();
		}
	}

报错：

总结： 
PreparedStatement只能用来为参数（如参数值）设置动态参数，即用?占位，不可用于表名、字段名等