字符转换

要把 Char 转成数字类型，需要显式转换:

• Use .code to get the numeric Unicode value of a character:

  val letter = 'A'

  println(letter.code) // 65
  

• If a character represents a decimal digit, use digitToInt():

  val digit = '7'

  println(digit.digitToInt()) // 7

   

   

   

  If the character may not be a valid digit, use digitToIntOrNull().