![]() ![]() When we create new instance by calling new PrintedDocument(), we create an object instance of PrintedDocument class in memory and have only memory space for PrintedDocument. This time, everything runs ok with neither compile error nor runtime error. PrintedDocument printedDoc = new Magazine() ![]() The problem will be found until codes gets run with an exception “Unable to cast object of type ‘PrintedDocument’ to type ‘Magazine’.”. Now, we have the other codes that do downcasting. Let give a very simple example of inheritance and we can use the example to explain how to use casting properly.Īs we see that Magazine is a derived class of PrintedDocument. However, I have seen some developers with problems of understanding when upcasting vs downcasting could be used even for Sr. In OOP, many developers know what inheritance is and how to do casting. ![]() We can access some specified methods of the child class.Īll the methods and variables of both classes can be accessed by performing downcasting.I try to explain what differences between upcasting and downcasting. The methods and variables of both the classes(parent and child) can be accessed. In the child class, we can access the methods and variables of the parent class. We can perform Upcasting implicitly or explicitly. ![]() The reference of the parent class object is passed to the child class. These are the following differences between Upcasting and Downcasting: S.NoĪ child object is typecasted to a parent object. Difference between Upcasting and Downcasting Downcasting is used when we need to develop a code that accesses behaviors of the child class. We use it when we need to develop a code that deals with only the parent class. Output: Why we need Upcasting and Downcasting? Child c = new Parent() // it gives compile-time error A method which prints the data of the parent class Here, the subclass object is referred by the parent class.īelow is an example of downcasting in which both the valid and the invalid scenarios are explained: Now the point is if downcasting is not possible in Java, then why is it allowed by the compiler? In Java, some scenarios allow us to perform downcasting. However, when we run it, it throws the "ClassCastException". In Java, we cannot assign a parent class reference object to the child class, but if we perform downcasting, we will not get any compile-time error. In Upcasting, we assign a parent class reference object to the child class. Upcasting is another type of object typecasting. Upcasting is also known as Generalization and Widening. We access only some specified variables and methods of the child class. Here, we don't access all the variables and the method. By using the Upcasting, we can easily access the variables and methods of the parent class to the child class. Upcasting is a type of object typecasting in which a child object is typecasted to a parent class object. Let's dive into deep of both these type of object casting: 1) Upcasting We can perform Upcasting implicitly or explicitly, but downcasting cannot be implicitly possible. In Upcasting and Downcasting, we typecast a child object to a parent object and a parent object to a child object simultaneously. Typecasting is used to ensure whether variables are correctly processed by a function or not. So, there are two types of typecasting possible for an object, i.e., Parent to Child and Child to Parent or can say Upcasting and Downcasting. Parent and Child objects are two types of objects. In Java, the object can also be typecasted like the datatypes. Next → ← prev Upcasting and Downcasting in JavaĪ process of converting one data type to another is known as Typecasting and Upcasting and Downcasting is the type of object typecasting. ![]()
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