scala學習筆記☞二：簡單文法練習

 1. var 和 val的差別

     A val is similar to a final variable in Java. so, once initialized ,that  can never be reasigned.

     A var is similar to a no-final variable in Java.

 2. define some functions;

     def max(x:Int,y:Int):Int={

          if(x>y)

             x

          else

            y

    }

    def: starts a function definition

    max: function name

   x:Int,y:Int  : parameter list in parentheses

   :Int   :  function's result type

Note： 1） scala's if expression  can result in  a value, So, It's similar to  java's ternary operator(x?y:z).

           2） sometimes the scala compiler will require you to specify the result type of a function. If the function don't has a result,but  you to specify unit tha is the result type . But, If the function is recursive ,for example , you must explicitly specify the function's result type.

 3. Array of the scala

    In scala,arrays are zero based,as in java, buy you access an element by specifying an index in parentheses rather than square brackets.

    eg: the first element  in a scala  array named steps in steps(0),not steps[0].

 4. comment of the scala

     as with Java.

 5. Loop with  While  and decide  with if

     1>  Java's i++ and ++i don't work in scala! To increment  in scala ,you need to say either i=i+1 or i += 1;

     2> You write while loops in scala in much the same  way  as in java.

 6. Iterate with foreatch and for

     eg:

   def main(args:Array[String])={

      var arg = Array("hello","scala","great");

      println(" 1:")

      arg.foreach((arg:String)=>print(arg+"   "))

      println

      println(" 2:")

      //要注明類型時需要括号，否則括号可省略。

      arg.foreach(arg=>print(arg+" "))

      println

      println(" 3:")

      //if a function literal consists of one statement that takes a single statement,

      //you need not explicitly name and specify the argument.

      arg.foreach(println)

      println("-----");

      for(argItem <- arg){//Note: argItem is a val.(not var)

        print(argItem+" ")

      }

   }