Diference between classes, traits, objects and packages
Classes in Scala are very similar to classes in Java. They are templates containing fields and methods. Like in Java, classes can be instantiated using the
new construct, there can be many “instances” (or “objects”) of the same class.
In Scala there exists a special kind of class named
case classes. You will learn about case classes during the course.
Classes in Scala cannot have static members. You can use objects (see below) to achieve similar functionalities as with static members in Java.
Traits are like interfaces in Java, but they can also contain concrete members, i.e. method implementations or field definitions.
Object in Scala are like classes, but for every
object definition there is only one single instance. It is not possible to create instances of objects using
new, instead you can just access the members (methods or fields) of an object using its name.
Adding a statement such as
package foo.bar at the top of a file makes the code in a file part of the package
foo.bar. You can then do
import foo.bar._ to make everything from package
foo.bar available in your code. The content of a package can be scattered across many files. If you define a
class MyClass in package
foo.bar, you can import that specific class (and not anything else from that package) with
In Scala, everything can be imported, not only class names. So for instance if you have an
object baz in package
import foo.bar.baz._ would import all the members of that object.