Scala第二章节

格式:  println(里边写你要打印到控制台的数据);

格式: print(里边写你要打印到控制台的数据);

println("Hello, Scala!")			//最后的分号可写可不写
//如果多行代码写在一行, 则前边语句的分号必须写, 最后一条语句的分号可以省略不写.
println("Hello"); println("Scala")	

//整型常量
println(10)
//浮点型常量
println(10.3)
//字符常量, 值要用单引号括起来
println('a')
//字符串常量, 值要用双引号括起来
println("abc")
//布尔常量, 值只有true和false
println(true)
//空常量
println(null)

int a = 0;

val/var 变量名:变量类型 = 初始值

scala> val name:String = "tom"
name: String = tom

scala> name = "Jim"
<console>:12: error: reassignment to val
       name = "Jim"

scala> var name:String = "tom"
name: String = tom

scala> name = "Jim"
name: String = Jim

scala> val name = "tom"
name: String = tom

val/var 变量名 = “字符串”

scala> println(name + name.length)
hadoop6

val/var 变量名 = s"${变量/表达式}字符串"

scala> val name = "zhangsan"
name: String = zhangsan

scala> val age = 23
age: Int = 23

scala> val sex = "male"
sex: String = male

scala> val result = s"name=${name}, age=${age}, sex=${sex}"
result: String = name=zhangsan, age=23, sex=male

scala> println(result)
name=zhangsan, age=23, sex=male

val/var 变量名 = """字符串1
字符串2"""

select
	*
from
    t_user
where
    name = "zhangsan"

val sql = """select
     | *
     | from
     |     t_user
     | where
     |     name = "zhangsan""""

println(sql)

lazy val/var 变量名 = 表达式

"""insert overwrite table adm.itcast_adm_personas
    select
    a.user_id,
    a.user_name,
    a.user_sex,
    a.user_birthday,
    a.user_age,
    a.constellation,
    a.province,
    a.city,
    a.city_level,
    a.hex_mail,
    a.op_mail,
    a.hex_phone,
    a.fore_phone,
    a.figure_model,
    a.stature_model,
    b.first_order_time,
    b.last_order_time,
      ...
    d.month1_hour025_cnt,
    d.month1_hour627_cnt,
    d.month1_hour829_cnt,
    d.month1_hour10212_cnt,
    d.month1_hour13214_cnt,
    d.month1_hour15217_cnt,
    d.month1_hour18219_cnt,
    d.month1_hour20221_cnt,
    d.month1_hour22223_cnt
    from gdm.itcast_gdm_user_basic a
      left join gdm.itcast_gdm_user_consume_order b on a.user_id=b.user_id
    left join gdm.itcast_gdm_user_buy_category c on a.user_id=c.user_id
    left join gdm.itcast_gdm_user_visit d on a.user_id=d.user_id;"""

scala> lazy val sql = """insert overwrite table adm.itcast_adm_personas
     |     select
     |     a.user_id,
	....
     |     left join gdm.itcast_gdm_user_buy_category c on a.user_id=c.user_id
     |     left join gdm.itcast_gdm_user_visit d on a.user_id=d.user_id;"""
sql: String = <lazy>

val b:Int = null

val/var 变量名:数据类型 = 具体的值.toXxx		//Xxx表示你要转换到的数据类型

val a:Double = 5.21
val b:Int = a.toInt

val/var 变量名:String = 值类型数据 + ""

val/var 变量名:String = 值类型数据.toString

val a1:Int = 10
val b1:Double = 2.1
val c1:Boolean = true

//方式一: 通过和空字符串拼接的形式实现
val a2:String = a1 + ""
val b2:String = b1 + ""
val c2:String = c1 + ""

//方式二: 通过toString函数实现
val a3:String = a1.toString
val b3:String = b1.toString
val c3:String = c1.toString

val/var 变量名:值类型 = 字符串值.toXxx	//Xxx表示你要转换到的数据类型

val s1:String = "100"
val s2:String = "2.3"
val s3:String = "false"

//将字符串类型的数据转成其对应的: Int类型
val a:Int = s1.toInt
//将字符串类型的数据转成其对应的: Double类型
val b:Double = s2.toDouble
//将字符串类型的数据转成其对应的: Boolean类型
val c:Boolean = s3.toBoolean

//1. 提示用户录入姓名.
println("请录入您的姓名: ")
//2. 接收用户录入的姓名.
val name = StdIn.readLine()
//3. 提示用户录入年龄.
println("请录入您的年龄: ")
//4. 接收用户录入的年龄.
val age = StdIn.readInt()
//5. 将用户录入的数据(姓名和年龄)打印到控制台上.
println(s"大家好, 我叫${name}, 我今年${age}岁了, 很高兴和大家一起学习Scala!")
为: " + str)

//1. 提示用户录入姓名.
println("请录入您的姓名: ")
//2. 接收用户录入的姓名.
val name = StdIn.readLine()
//3. 提示用户录入年龄.
println("请录入您的年龄: ")
//4. 接收用户录入的年龄.
val age = StdIn.readInt()
//5. 将用户录入的数据(姓名和年龄)打印到控制台上.
println(s"大家好, 我叫${name}, 我今年${age}岁了, 很高兴和大家一起学习Scala!")