scala笔记

scala

package song.study.scala
object Caculator{
  def Add(x:Int,y:Int):Int = {
    x + y
  }
}
object FirstApp {
  def main(args:Array[String]):Unit = {
    try{
      var half = -1;
      var c = if (half >0) 2 else throw new RuntimeException("half <0")
      println(c)
    }catch{
      case e:Exception => println("The Excetion is " +  e.printStackTrace()); 
    }
    println(Caculator.Add(1, 2))
  }
  def doWhile(){
    var line = ""
    do{
      line = readLine()
      println("Read:" + line)
    }while(line != "")
  }
}

tuple,array,map

package song.study.scala
object Caculator{
  def Add(x:Int,y:Int):Int = {
    x + y
  }
}
object FirstApp {
  def main(args:Array[String]):Unit = {
    //Tuple
    var pair = (100,"a","b","c")
    println(pair._1);
    //Array
    var array = Array(1,2,3,4,5)
    for(i<-0 until array.length){
      println(array(i));
    }
    for(elment <- array){
      println(elment)
    }
    //map
    var countrys = Map("China"->142,"USA"->150)
    for((k,v) <- countrys)
    {
      println("Key:" +  k + ",Value:" +  v)
    }
    for((k,_) <- countrys){
      println("Key:" +  k + ",Value:" +  countrys(k))
    }
    countrys.keys.foreach { k => 
      println("Key:" +  k + ",Value:" +  countrys(k))
    }
  } 
}

for循环条件

    for(i <- 1 to 5;j <- 1 to 5 if i !=j){
      println("-----------------")
      println("I:" + i)
      println("I:" + j)
      println("-----------------")
    }

匿名方法,默认参数,返回值,可变参数,递归函数等

     def addA(x:Int) = x + 100 //普通方法方法可以自动判断类型,但是如果用在递归的时候必须指明返回值
    def addA(x:Int):Int =  if(x <=0) 1 else x * addA(x-1) //用了递归所以必须增加返回值
         def combine(x:Int,y:Int = 1,z:Int=3) = x + y + z //默认参数值
     val add = (x:Int) => x + 200 //匿名方法
         def connected(args:Int*)={ //可变参数
      var result = 0
      for(arg <- args) result += arg
      result 
    }
     println(addA(1))
     println(add(2))

Scala中val和var的区别

Scala有两种变量，val和var。val就不能再赋值了。与之对应的，var可以在它生命周期中被多次赋值。

lazy

lazy延迟加载,file增加了lazy,那么延迟到使用的时候再去实例.
其实test1这个文件并不存在,但是代码执行没错,因为加了lazy所以代码并未执行.
如果去掉lazy那么执行就会报错
lazy val file = Source.fromFile("E:\text1.txt")