第4节：Scala控制结构if..else,for,while,breakable

控制结构在spark源码中的鉴赏

 

 

none 省写的话默认是（）是返回any类型，而none是optional类型。

 

 

 

 

 

case object None extends Option[Nothing] {
  def isEmpty = true
  def get = throw new NoSuchElementException("None.get")
}

 

package com.dt.spark.scala.bascis

object ControlStructures {
    def main(args: Array[String]): Unit = {
     println("scala") 
     
     var age =30
     //if else 有值的，而java中if没有值的
     println (if (age >25 ) "Worker"  else "student")
     
    val  result = if (age >25 ) "Worker"  else "student"
    println(result)
    //val result2: Any 是 字符串和整型的父类any
    // if条件表达式进行类型推断
    val result2 = if (age >18 ) "adult " else 1 
    println(result2)
     //val result3: Any
     val result3 = if (age >58 ) "adult "
       println(result3 )
       //val result33: Any result3全写的写法
       //默认 ()空值表示 unit
     val result33 = if (age >48 ) "adult " else ()
  println(result33)
  
       val result4 = if (age >48 ) "adult " else None
    }
}

 

运行结果

scala
Worker
Worker
adult 
()
()

 

 

 

 

object ControlStructures {
  def main(args: Array[String]): Unit = {
    println("scala")

    var age = 10
    //if else 有值的，而java中if没有值的
    println(if (age > 25) "Worker" else "student")

    val result = if (age > 25) "Worker" else "student"
    println(result)
    //val result2: Any 是 字符串和整型的父类any
    // if条件表达式进行类型推断
    val result2 = if (age > 18) "adult " else 1
    println(result2)
    //val result3: Any
    val result3 = if (age > 58) "adult "
    println(result3)
    //val result33: Any result3全写的写法
    //默认 ()空值表示 unit
    val result33 = if (age > 48) "adult " else ()
    println(result33)

    val result4 = if (age > 48) "adult " else None

    var x, y = 0
    val result5 = if (age < 18) {
      x = x + 1
      y = y + 1
      x + y
    } else 0
    println(result5)
    println("==================")
    for (i <- 0 to 5 if i == 2) {
      println(i)
    }

    var flag =true
    var sum=0
     for (i <- 0 to 6 if flag) {
       sum = sum + i
       if (5 == i ) flag =false
      
    }
    println("sum:  "+sum)
    
    for (item <-"hello spak") println(item)
    
     for (item <-"hello spak".split(" ")) println(item)
    
  }
}

 

 

scala
student
student
1
()
()
2
==================
2
sum:  15
h
e
l
l
o
 
s
p
a
k
hello
spak

 

 

 

 for循环中能够提取出什么内容取决于后面集合的类型！！！ 

 

object ControlStructures {

  def main(args: Array[String]): Unit = {
    println("scala")

    var age = 10
    //if else 有值的，而java中if没有值的
    println(if (age > 25) "Worker" else "student")

    val result = if (age > 25) "Worker" else "student"
    println(result)
    //val result2: Any 是 字符串和整型的父类any
    // if条件表达式进行类型推断
    val result2 = if (age > 18) "adult " else 1
    println(result2)
    //val result3: Any
    val result3 = if (age > 58) "adult "
    println(result3)
    //val result33: Any result3全写的写法
    //默认 ()空值表示 unit
    val result33 = if (age > 48) "adult " else ()
    println(result33)

    val result4 = if (age > 48) "adult " else None

    var x, y = 0
    val result5 = if (age < 18) {
      x = x + 1
      y = y + 1
      x + y
    } else 0
    println(result5)
    println("==================")
    for (i <- 0 to 5 if i == 2) {
      println(i)
    }

    var flag =true
    var sum=0
     for (i <- 0 to 6 if flag) {
       sum = sum + i
       if (5 == i ) flag =false
      
    }
    println("sum:  "+sum)
    
      sum=0
     for (i <- 0 to 6 ) {
       sum = sum + i
    //   if (5 == i ) return // return 返回的是方法级别的，后面也不打印了
      
    }
    println("sum return :  "+sum)
    
    
    
    for (item <-"hello spak") println(item)
    
     for (item <-"hello spak".split(" ")) println(item)
    // for 循环用守卫
     //while 用flag
     import scala.util.control.Breaks._
     flag =true
     breakable {
        while ( flag ) {
       for (item <- "spark") {
          println ("while item======="+item)
          if (item == 'r') {
            flag = false
            break
          }
          
       }
     }
     }
    
      println ("over")
     
     
  }
}