Scala's first Scala program

Scala's first Scala program

We can execute Scala code and compile it scalac the scalac command line tool.

object HelloWorld { 
    def main(args: Array[String]) { 
        println("Hello,World!") 
    } 
} 

Attention

The sign at the end of the statement is usually optional.

The sign at the end of the statement is usually optional.

Scala program processing starts with the main method, which is a mandatory part of each Scala program.

The primary method is not marked as static.

The primary method is the instance method for the automatic instantiation of single-case objects.

No type was returned. There is actually Unit, which is similar to void, but it is inferred by the compiler.

We can explicitly specify the return type by adding a colon and type after the argument:

def main(args: Array[String]) : Unit = { 
} 

Scala uses the def to tell the compiler that this is a method.

There are no access-level modifiers in Scala.

Scala does not specify a public modifier because the default access level is public.

Print some numbers

Let's write a program that prints numbers from 1 to 10 in Print1.scalafile:

object Main {
  def main(args: Array[String]) {
        for {i <- 1 to10} 
          println(i) 

  }
}

We can enter scala Main.scala to run the code

The program assigns numbers 1 to 10 to variables, then performs println(i) and prints numbers 1 to 10.

In the Print2.scala file, put in

object Main {
  def main(args: Array[String]) {
        for {
           i <- 1 to 10 
             j <- 1 to 10
        } 
        println(i* j) 

  }
}