给student添加两个方法 Study和Sleep(注意首字母大写)

TableName 唯一指定表名

TableName 唯一指定表名

Value 实现 driver.Valuer 接口

Value 实现 driver.Valuer 接口

Value 实现 driver.Valuer 接口

Value 实现 driver.Valuer 接口

闭包的写法：函数里面嵌套一个函数，最后返回里面的函数就形成了闭包

闭包的写法：函数里面嵌套一个函数，最后返回里面的函数就形成了闭包

Obtain the number of bytes (not characters) in the given argument. TODO: Add the `AsRef` trait appropriately as a trait bound.

TODO: Write a function that calculates the price of an order of apples given the quantity bought.

TODO: Apply the `capitalize_first` function again to a slice of string slices. Return a single string. ["hello", " ", "world"] -> "Hello World"

TODO: Apply the `capitalize_first` function to a slice of string slices. Return a vector of strings. ["hello", "world"] -> ["Hello", "World"]

Obtain the number of characters (not bytes) in the given argument. TODO: Add the `AsRef` trait appropriately as a trait bound.

TODO: Fix the compiler error by only changing the signature of this function.