Lecture #1 9/2
授课时间：2020-09-02 13:50:00

Scala Basics

Hello Scala!

Example:

package week1.basics 
object Hello{
    def main(args: Array[String]): Unit = {
        println("Hello Scala!")
    }
}

package week1.basics : define where this code lives.
object Hello: Objects
def main{}: Main Method
println("Hello Scala!"): Print Line

Methods Variables

package week1.basics
object FirstObject{
    def multiplyBtTwo(input: Double): Double = {
        input * 2.0
    }

    def main(args: Array[String]): Unit = {
        var x: Double = 7.0
        var result = multiplyBtTwo(x)
        println(result)
    }
}

input: input value
Double: Data type
Usually no return statements.

var: Variables declaration

Conditionals

package week1.basics
object Coditional{
    def computeSize(inout: Double): String = {
        val large: Double = 60.0
        val medium: Double = 60.0
        if (input >= large) {
            "large"
        } else if (input >= medium) {
            "medium"
        } else {
            "small"
        }
    }

    def main (args: Array[String]): Unit = {
        println(computeSize(70.0))
        println(computeSize(50.0))
        println(computeSize(10.0))
    }
}

val: Values declared with val cannot change, Reassignment causes an ERROR!
"small": means return "small"

Lecture Question

Question

In a package named “lecture” create an object named “FirstObject” with a metho named “computeShippingCost” that takes a Double representing the weight of a package as a paramater and returns a Double representing the shipping cost of the package.

Ex:
The shipping cost is ($)5 + 0.25 per pound over 30