Comments on Casting

• Casting (type conversion) is supported between types and class types. Syntax:

  • (classname)reference

• Two forms of casting are possible: widening and narrowing

• Widening, where the subclass is used as an instance of the superclass, is performed implicitly

• Narrowing, where the superclass is used as an instance of the subclass, must be performed explicitly

• Given Parent: Dot -> DrawableDot (Child):

  • Widening: An instance of DrawableDot is used as an instance of Dot
  • Narrowing: An instance of Dot is used as an instance of DrawableDot

• Casting between sibling classes is a compile-time error

Previous slide

Next slide

Back to first slide

View graphic version