Scala Hello World

原创转载请注明出处：http://agilestyle.iteye.com/blog/2331800

 

HelloScala.scala 

package org.fool.scala.helloworld

object HelloScala {
  def max(x: Int, y: Int): Int = {
    if (x > y) x
    else y
  }

  def greet() = println("Hello World")

  /*
    Scala has two kinds of variables, vals and vars.
    A val is similar to a final variable in Java.
    Once initialized, a val can never be reassigned.
    A var, by contrast, is similar to a non-final variable in Java.
    A var can be reassigned throughout its lifetime.
  */
  def testValAndVar() = {
    val msg = "Hello Val"
    println(msg)

    var msg2 = "Hello Var"
    println(msg2)

    msg2 = "Hello Var again"
    println(msg2)
  }

  def main(args: Array[String]): Unit = {
    // Hello World
    println("Hello World")

    // Hello World
    greet()
    /*
      Hello Val
      Hello Var
      Hello Var again
    */
    testValAndVar()

    // Hello, Spark
    println("Hello, " + args(0))

    // Spark Hadoop MapReduce HDFS
    var i = 0
    while (i < args.length) {
      print(args(i) + " ")
      i += 1
    }
    println()

    // Spark Hadoop MapReduce HDFS
    args.foreach(arg => print(arg + " "))

    println()

    /*
      Spark
      Hadoop
      MapReduce
      HDFS
    */
    args.foreach(println)

    // Spark Hadoop MapReduce HDFS
    for (arg <- args) print(arg + " ")

    println()

    // 3
    println(max(2, 3))
    // -2
    println(max(-2, -3))
  }
}

Pogram arguments

 

Console Output