What is the default “type” of parameters in scala? Is it Val?

Question

I have a simple class like this.

I haven't specified whether the parameters are val's or var's. What type of parameters are name and price ?

 class Car(name:String, price:Float){ 
 }

Answer 1

The accepted answer is right in principle. In practice, however, if the passed parameter is used in the implementation of a def , it will become an instance field, acting pretty much as if declared using private val (except that no private def getter will be generated for it).

For example:

class Foo(bar: Bar) {
    def foo: Bar = bar
}

can be decompiled into the following java translation (using javap )

public class Foo {
  private final Bar bar;
  public Bar foo();
  public Foo(Bar);
}

See also my answer on this thread for more details about this.

Answer 2

If you declare a class parameter as either var or val , it will become an instance variable. If you don't specify either, it won't. So it's not equivalent to either val or var .

In terms of whether or not they can be re-assigned, class parameters act just like normal parameters, which can't be re-assigned.

Answer 3

Adding to the answer by @sepp2k : If you use a case class then the default is val :

 case class Foo(bar: Bat)

in this case bar is a val that is of public accessibility.