println("hello world");val x = 1+1;println(x);//val 不允许再次赋值    //x = 3;//变量varvar xx = x;xx = xx+1;println(xx);//blocks{  var xxx = 12;  println(xxx);}//Functions//Functions are expressions that take parameters.(x:Int)=>x+1;//name Functions//use varvar addOne =  (x:Int)=>x+1;println(addOne(12));addOne = (x:Int) => x+2;println(addOne(12));//use valval addOneVal = (x:Int)=>x+1;println(addOneVal(12));//error reassignment to val// addOneVal = (x:Int)=>x+2;// println(addOneVal(12));//method//method Methods look and behave very similar to functions, //but there are a few key differences between them.//Methods are defined with the def keyword. //def is followed by a name, parameter lists, //a return type, and a body.def add(x:Int):Int = x;println(add(12));def addTwo(x:Int)(xxx:Int):Int = {  //return not must need  return xxx+x;}println(addTwo(12)(13));def addTwo(x:Int,y:Int)(xxx:Int) : Int = {  //return not must need  //  //The last expression in the body is the method’s return value.   //Scala does have a return keyword, but it’s rarely used.   x+y-xxx;}println(addTwo(12,12)(13));//no paramdef name : String = {  System.getProperty("user.name");}println("name="+name);class Test(name:String,money:Double){  def call(youName:String):Unit=  {    println("name="+name);    println("money="+money);    println("youName="+youName);    println("\n");  }}var test1 = new Test("kk1",10D);test1.call("zzz1");val test2 = new Test("kk2",10D);test2.call("zzz2");//reassignment to val//test2 = test1;var test3 = new Test("kk3",10D);test3.call("zzz3");test3 = test2;test3.call("zzz3");test3 = test1;test3.call("zzz3")//case class//Scala has a special type of class called a “case” class. //By default,case classes are immutable and compared by valuecase class Point(x:Int,y:Int)val p1 = new Point(1,2)val p2 = new Point(1,3)var p3 = new Point(1,2)if(p1==p2)println("p1 eq p2 "+"p1="+p1+" p2="+p2)elseprintln("p1 neq p2 "+"p1="+p1+" p2="+p2)if(p1==p3)println("p1 eq p3 "+"p1="+p1+" p3="+p3)elseprintln("p1 neq p3 "+"p1="+p1+" p3="+p3)case class Point2(x:Int,y:Int){   def test(xx:Int):Int=   {     println("here")     x+xx   }}val pp2 = new Point2(12,13);println(pp2.test(100));//Objects are single instances of their own definitions. //You can think of them as singletons of their own classes.//定义的实例是对象object Test2{  def call(x:Int):Int = x+100}println(Test2.call(100));val ttt = Test2.call(100)println(ttt)var ttt2: Int = Test2.call(100)println(ttt2);val ttt3: Int = Test2.call(100)println(ttt3);//Traits are types containing certain fields and methodstrait Interface{  val xx = (x:Int)=>x+1  var xxx = (x:Int)=>x+2  var xi:Int = 0 def  test(x:Int,y:Int):Unit = {   println(x) }}//trait Interface is abstract; cannot be instantiated//val i = new Interface();// val i = new Interface();// println(i.test(11,11));println("\n\n");class DefaultIntereface extends Interface{  override def test(x:Int,y:Int) : Unit =  {    println(xx(x));    println(xxx(x));    xxx = xx;    xi = x;    println(x);  }} val i = new DefaultIntereface(); i.test(1,1); println("\n\n"); //value k is not a member of  //ScalaFiddle.this.DefaultIntereface// if(i.k==null)// println(i.test(11,11)) i.test(1,1)println("\n\n");println(i.xi) i.xi = 12; println(i.xi)   //The main method is an entry point of a program object Main {  def main(args:Array[String]):Unit=  {    println("this is Main")    } }   Main.main(null);

val和var的区别

val是值，不可变

var是变量，可变

函数只是过程，函数定义语法

[var-val] = (paramName:paramType,paramName:paramType) => process

方法,方法和函数类型,有以下不用

使用def 关键字定义,有名字,有参数列表,有返回值,scala有return关键字,但它不是必须的,默认最后一行的计算结果就是返回值

def methodName(paramName:paramType) : returnType ={

}

Class

class ClassName(paramName:paramType){

//method

}

//make an instance of a class

val greeter = new Greeter("Hello, ", "!") case class case class是特别的类型,它不可变,通过值比较 Objects 对象是根据定义生成的实例,语法如下 object ObjectName { //field //method } 对象不可new traits,traits包含方法和字段 traits traitsName { //field 　　//method,方法可以有默认实现 //如果实现traits的实现重载traits里面的方法,必须要有override 　 }