Downcasting permits an object of a superclass type to be treated as an object of any subclass type.
Questions tagged [downcast]
589 questions
1
vote
1 answer
Terse way to downcast container contents
I'm frequently finding myself doing something like:
val json:Map[String,Any] = getJSON(...)
val v = json.get("username")
val uname = if ( v!=null ) v.asInstanceOf[toString] ) else null
whereas what I'd much prefer to write is:
val uname =…
user48956
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4 answers
Downcasting safety
Here's the code:
Base b = new Derived(); // Upcasting
// Some actions
Derived d = (Derived)b; // Downcasting
As I understand the reference is like stencil through which you're looking at some chunk of memory. And upcasting just narrows that…
Paul Kyrejto
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7 answers
Downcasting objects in Java
class A{
}
public class Demo
{
public static void main(String s[])
{
Object o=(Object) new Demo();
if (((A)(o)) instanceof Object)
{
System.out.println("true");
}
}
}
I am getting Exception…
Akhilesh Dhar Dubey
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2 answers
public interface introduced in derived class
Two classes, D1 and D2 derive from an abstract base class B. Each of them share common public interface declared in B but each of them might also have their own specific public interface (e.g. D2 has D2.Bar() which makes sense only for D2…
Bojan Komazec
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4 answers
Calling ungeneric methods from generic method in java
Consider the following:
public class Doer {
public static void doStuff(A a) {
System.out.println("a");
}
public static void doStuff(B b) {
System.out.println("b");
}
}
Where B extends A
And a generic class like this:
public…
Nathalie De Crop
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vote
1 answer
systemverilog cast peculiarity
My question is regarding using $cast in SV.
If you search for the word cast in the code below, I have on purpose added a '!' to check for unsuccessful casting. In the event of unsuccessful cast, I wanted to see what happens when a call is made to…
V from QC
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- 1
1
vote
2 answers
Java downcasting with reflection
I hava a model in Java 1.6 similar to this example:
public class Animal {
public String color;
}
public class Dog extends Animal {
public Float height;
}
public class Bird extends Animal {
public Integer wings;
}
Now I want cast from Animal…
earnaz
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1
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1 answer
downcasting in php5
I've realized that there's no downcasting in php5. Is there a common pattern to achieve it?
cort
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1
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2 answers
scala downcasting with generics
I'm looking for help with the following problem:
case class A(val name: String)
class B(name: String) extends A(name)
class Base[T <: A](param: T)
class SubClass[T <: B](param: T)
object Factory {
def create[T <: A](param: T) = {
param.name…
user1467422
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1
vote
6 answers
java use object as double without explicit cast
Say I have this:
Object obj = new Double(3.14);
Is there a way to use obj like a Double without explicitly casting it to Double? For instance, if I wanted to use the .doubleValue() method of Double for calculations.
Mastergeek
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6 answers
Down Casting in Java
Can anyone here please explain to me why I get a java.lang.ClassCastException when downcasting a Parent to a Child?
public class Child extends Parent{
public static void main(String[] args){
new Child().go();
}
void go(){
go2(new Parent(),…
user1369311
1
vote
3 answers
How to avoid too many downcasts in a function
I have too many downcasts in my code. In c++ I can use templates to avoid downcasting. But what is the best implementation of the following example in c#?
class Pet { bool mIsDog; }
class Dog : Pet // mIsDog = true
class Cat : Pet // mIsDog =…
Fan
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2 answers
how i can reduce the digits after the decimal point?
I need only up to two decimal points.
Dim v1, v2, v3, v4, v5, tv, rp1, rp2, rp3, rp4, rp5 As Double
Dim Per1, Per2, Per3, Per4, per5 As Double
Per1 = v1 / tv * 100
Per2 = v2 / tv * 100
Per3 = v3 / tv * 100
Per4 = v4 / tv * 100
…
sangeen
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2 answers
Java: Casting ParentClass and ChildClass (Downcast Runtime Error)
public class InheritanceDemo {
public static void main(String[] args) {
ParentClass p = new ParentClass();
ChildClass c = new ChildClass();
//Casting ChildClass to ParentClass
ParentClass pc = new…
SpiritOfDragon
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1 answer
Implicit downcast from 'System.IO.Stream' to 'System.IO.MemoryStream'
function SerializeObject(pObject : Object)
{
var XmlizedString : String = null;
var memoryStream : MemoryStream = new MemoryStream();
var xs : XmlSerializer = new XmlSerializer(typeof(XmlData));
var xmlTextWriter : XmlTextWriter = new…
smeddles24
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