Note, that data will not be lost, you just can’t use it, until you downcast the object to the right level. Learn about Upcasting and Downcasting in Java Full tutorial with concrete examples. Dog d new Dog () Animal a d // Upcasting a.getAnimalName () Here a.getAnimalName () calls the subclass's getAnimalName () method, as it is inherited from base class, so the parent class's method is called. In this article, we will look at the details of DownCasting. When you refer your subclass with parent class, method call on reference pointer calls the subclass method. For example, if you cast a Cat to an Animal, it will lose properties inherited from Mammal and Cat. Upcasting and Downcasting in Java - Full Tutorial. We can implicitly or explicitly perform the UpCasting, but we can only perform DownCasting explicitly. If you upcast an object, it will lose all it’s properties, which were inherited. Object slicing is defined as the conversion of an object into something with less information (typically a superclass) More detail Once I downcast it, then I can do compareAccount.accountAmount. When I do account1.equals (account2) I have to downcast account2 in the equals () method back to its subclass reference BankAccount compareAccount (BankAccount)obj so that I have access to the child classes fields. Upcasting is always typesafe but can cause the so called “slicing” problem. Downcasting and upcasting objects and dynamic method binding. Upcasting is done automatically, while downcasting must be manually done.Īnimal a = c1 //automatic upcasting to AnimalĬat c2 = (Cat) a //manual downcasting back to a Cat Java permits an object of a subclass type to be treated as an object of any superclass type.
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