Upcasting permits an object of a subclass type to be treated as an object of any superclass type.
Questions tagged [upcasting]
244 questions
8
votes
2 answers
In Java, why does type casting of a character to an integer NOT extend the sign bit
In Java a bitwise operation causes type casting to integer and also causes sign extension. For instance the following is expected:
byte b = -1;
System.out.println(b >> 1);//-1
In Java chars are encoded in UTF-16 and each unit is represented with 2…
CEGRD
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Does up casting in Java hide the subclass methods and fields?
On the program I'm writing I have a class RestrictedUser and class User that is derived from RestrictedUser. I'm trying to hide the User specific methods by casting to RestrictedUser but when I do the casting the User methods are still available.…
tatsuhirosatou
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8
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Placement new and inheritance
Good evening everyone.
A code snippet will be worth a thousand words :
// Storage suitable for any of the listed instances
alignas(MaxAlign::value)
char storage[MaxSize::value];
// Instanciate one…
Quentin
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8
votes
1 answer
what is "upcast"?
I can see that the term "upcast" is related to OOP, but I can't find the exact definition by searching the Internet.
Could anyone explain what does the term mean and in what situation this technique useful?
can.
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5 answers
Cost of Up-casting to ArrayList of objects and then down-casting to custom ArrayList
I have a situation in which I am getting data from database, and I want to upcast it to ArrayList of objects and then downcast it to different custom ArrayList i.e. List, List etc.
My question is up-casting to object and then…
Androider
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7
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How to cast object to its actual type
Consider the following piece of code:
class MyClass
{
}
class MyClass2 : MyClass
{
}
private void Foo(MyClass cl)
{
//cl is actually MyClass2 instance
TestGeneric(cl);
}
private void TestGeneric(T val)
{
//do smth
}
After calling…
Gena Verdel
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C++ - upcasting and downcasting
In my example:
At upcasting, shouldn't the second d.print() call print "base"?
Isn't it "d" derived object upcasted to a base class object?
And at downcasting, what advantages does it have?
Could you explain upcast and downcast in a practical…
Mihai
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Use a function with an argument of a derived type (F#)
I've got a class in my application - for simplicity let's assume it's defined like this:
type baseType() =
member this.A = 5.
Also, I've got a lot of functions that take objects of this type as an argument. Moreover, some of them take an array…
LA.27
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5
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up-casting in C# and call a specific method based on the derived type
I have a couple of classes, all derived from the same base type.
class basetype{}
class TypeA : basetype{}
class TypeB : basetype{}
...
A number of them is stored in a list.
List myObjects
As always, each of these types has to be handled…
Alexander
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Is overriding toString() considered polymorphism?
I was having an exam in Java today and the examiner asked me if I can provide any examples of using polymorphism in my Spring Boot project.
As I couldn`t think of anything at first, he pointed out that I have overriden toString() in my models and…
Petar Bivolarski
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5
votes
7 answers
Upcasting when making object
Say you have a Shape base class and various derived types: Circle, etc.
Is there ever any reason to upcast right there when making a new object, by writing this:
Shape s = new Circle();
instead of this:
Circle s = new Circle();
and are the s…
Jean-François Corbett
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5
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3 answers
why overridden method calling from Subclass if i have done up-casting?
i have just started learning java::Inheritance and confused while mixing Up-Casting.
class Example{
public void methodOne(){
System.out.println("Example::Method_1");
}
public void methodTwo(){
…
Avinash Kumar
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5
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1 answer
Cast for upcasting only
We all know that C-style casts are considered evil in C++. Which is why they are replaced by const_cast<>, static_cast<>, and dynamic_cast<> to provide for more bespoke casting, allowing the programmer to only allow the intended classes of…
cmaster - reinstate monica
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C#: Superclass still has subclass info after upcast
I have 2 types: BaseQuestion and Question. Question inherits some properties from BaseQuestion. Now I have created a Web API to make a BaseQuestion available. The Question datatype has additional properties that I do not want to make available. I…
Jan
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What are the undesirable results the author is talking about?
This example was taken from Bruce Eckel's "Thinking in C++" Chapter 14, Section "Upcasting and the Copy Constructor".
#include
using namespace std;
class Parent
{
int i;
public:
Parent(int ii) : i(ii) { cout << "Parent(int…
Belloc
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