code snippet-01

more https://github.com/yuqingwang15/scala-coding

01break 用法

// (x:Int, y:Int) => x+y
import scala.util.control.Breaks._
object test { 
def main(args:Array[String]){ 
println("hello test") 

breakable{ 
for(i<-0 to 10){ 
if(i==5) break 
println(i)
} 
} 
println(test2)
} 
def test2():Int={ 
return 1 
} 
} 
//breakable

 

02 Symbol定义

// `x
final case class Symbol private (name:String){
override def toString(name:String):String = "`" + name
}
/* 
see the toString(name:String) as a funcname and the return type is string
give the funcname value : "`" + name
override just point out that this func have some relation with others
class is a object containing a func-object and a parameter
*/

 

03多行输出

"""the present string
spans three
lines."""

 

04 case

//null scala.Null
//与每个引用类型兼容。它表示引用一个特殊的“null”对象的参考值。

//abstract works with extends
//case works with extends abstract class , sons of abstract class
//class has parameters with types
//object JNull

abstract class JSON
case class JSeq(elems: List[JSON]) extends JSON
case class JNum(elems: Double) extends JSON
case class JStr(elems: String) extends JSON
case class JBool(elems: Boolean) extends JSON
case class JObj(bingdings: Map[String, JSON]) extends JSON
case object JNull extends JSON
type JBinding = (String , JSON)

// a match{case ab ; case ac ..}
//=> do what,instructions = is what,defination
//

class tjson {
  def show(json :JSON) :String= json match{
    case JNum(num) => num.toString
    case JStr(str) => "\""+str +"\""
    case JBool(b) => b.toString
    case JSeq(seq）=>"["+  (seq map show mkString  ",")  +"]"
    // binding is what :map from (k,v) to String 
    case JObj(bindings) => 
      val obj = bindings map{
        case (key ,value) =>"\"" +key+"\":" + show(value)
      }
    case JNull =>"null"
  } 

 

05单例

import java.io_

class Point(val xc:Int,val yc:Int){
var x:Int = xc
var y:Int = yc
//val ->var

def move(dx:Int, dy:Int) {
x = dx+x
y = dy+y
}

}

object Demo{
def main(args:Array[String]){
val point = new Point(10,20)
printPoint

def printPoint{
println("Point x location:" + point.x)
}
}
}

 

06loop

object Run {
implicit class IntTimes(x: Int) {
def times [A](f: =>A): Unit = {
def loop(current: Int): Unit =

if(current > 0){
f
loop(current - 1)
}
loop(x)
}
}
}

import Run._

object Demo {
def main(args: Array[String]) {
4 times println("hello")
}
}