Packaging

The classes in the same package are visiable to each other, and accessable by their names.

The classes in the different packages are not accessable unless we import them or use the fully qualified name.

package prj1.demo1

import prj2.demo2

object Demo1 extends App {
  val demo2 = new Demo2Test
  val demo3 = new prj3.Demo3Test
}

Package Object

It's created for universal constants or methods for a package.

Each package has only ONE package object.

Import

import java.util.Date

val date = new Date

If you want to use java.sql.Date at the same time, there are 2 ways.

1. use fully qualified name

   val sqlDate = new java.sql.Date(2021, 12, 28)
   

2. use aliasing

   import java.sql.{Date => SqlDate}
   

Multiple Imports

You can import multiple classes from the same package by:

import zoo.{Cat, Dog}

Default Imports

• java.lang: String, Object, Exception, etc
• scala: Int, Nothing, Function, etc
• scala.Predef: println, ???, etc