In Scala, difference between final val and val [duplicate]

final members cannot be overridden, say, in a sub-class or trait.

Legal:

class A {
    val a = 1
}

class B extends A {
    override val a = 2
}

Illegal:

class A {
    final val a = 1
}

class B extends A {
    override val a = 2
}

You’ll get an error such as this:

:9: error: overriding value a in class A of type Int(1);

value a cannot override final member