Upcasting and downcasting in Java and polymorphism Asked 2 years, 8 months ago Modified 2 years, 3 months ago Viewed 455 times
248 Upcasting is casting to a supertype, while downcasting is casting to a subtype. Upcasting is always allowed, but downcasting involves a type check and can throw a ClassCastException. In your case, a cast from a Dog to an Animal is an upcast, because a Dog is-a Animal.
1 To do downcasting in Java, and avoid run-time exceptions, take a reference of the following code: ... Here, Animal is the parent class and Dog is the child class. instanceof is a keyword that is used for checking if a reference variable is containing a given type of object reference or not.
I can understand what upcasting is but downcasting is a little confusing. My question is why should we downcast? Can you help me with a real world example ? Is downcasting that important?
Below is a full textual information for the same. “Upcasting” means moving subclass object to the parent class object. “DownCasting” is opposite to “Upcasting” moving the parent object to the child object. “Upcasting” is perfectly valid but “Downcasting” is not allowed in .NET.
Eu sei que Upcasting é converter um objeto da subclasse para a superclasse e Downcasting é converter um objeto da superclasse para a subclasse. Mas em relação a perda de valores e esses afins, com...
Upcasting in Java, and many other OOP languages, is never necessary - it happens automatically during the assignment. Such as, person2 = person3; . This is a fundamental concept in Object Orientation: Inheritance. Inheritance describes an "is a" relationship. In your example, TeacherAide is a Teacher because TeacherAide inherits from Teacher.