Because you are passing the classes by const reference, I assume you want to copy them. For that you will need additional virtual member function clone which will return a pointer to a dynamically allocated copy of the object. class func { … virtual func* clone() const; … }; class polynom: public func { … … Read more
While your question indicates it’s for “general OO”, it really seems to be focusing on .NET use of these terms. In .NET (similar for Java): interfaces can have no state or implementation a class that implements an interface must provide an implementation of all the methods of that interface abstract classes may contain state (data … Read more
No. A class with an incomplete implementation must be declared abstract. It cannot be directly instantiated, but it can serve as a common base for subclasses to build upon. The point of all this is that the compiler can make sure that when a method is called on an object (as defined by the interface), … Read more
An abstract class is a class that cannot be instantiated and must be extended by child classes. Any abstract methods in an abstract class must be implemented by an extending child class (or it must also be abstract). It’s possible to have an abstract class without abstract methods to be implemented; but that’s not particularly … Read more
The reason we have default methods in interfaces is to allow the developers to add new methods to the interfaces without affecting the classes that implements these interfaces. Here is link for complete article. 0 solved Why can I define only default and static methods inside a java interface? [duplicate]
Your PrintDetails() method is printing the array without any kind of formatting (hence it’s just printing the array type) use string.Join to print the array delimenated by commas public override void PrintDetails() { Console.WriteLine(“Hi my name is ” + _name + ” and I am studying ” + string.Join(“,”, _subjects)); } ought to do it. … Read more
Alright let’s see. First you call Circle9() that starts the constructor: /** No-arg constructor */ public Circle9() { this(1.0); System.out.print(“C”); } As you can see the constructor first calls this(1.0) This means that another constructor is opened and afterwards we print “C” Alright the next Constructor is: public Circle9(double radius) { this(radius, “white”, false); System.out.print(“D”); … Read more
us is a variable of type (class) NumberFormat. getCurrencyInstance() is a static method (a method of the class, not of an object). So this method is not related to a object. But this method generates an object of class NumberFormat (a kind of factory), that is stored in the variable us. now that you have … Read more
The class Derived is still abstract since the pure virtual function Base::foo hasn’t been overridden. solved Abstract class without defining in derived class
Since you need to adapt to different mechanics\protocols, you can implement Adapter pattern. Also, adapter can be chosen at runtime, you can also implement Factory pattern to instantiate an adapter. And then Strategy pattern to have adapters and factories. All this being done with IoC to inject dependencies like adapters or factories solved Abstract Factory … Read more
So, blah defines an instance field called label but does not initialise it public abstract class Blah { protected JLabel label; } BlahChildOne initialises the label from Blah public class BlahChildOne extends Blah { public BlahChildOne() { label = new JLabel(); } } BlahChildTwo does not initialises the label from Blah, so it is still … Read more
From a programming perspective, there isn’t really anything wrong with the code. I guess what your teacher was getting at is that Fluffy should be an interface and Animal should be the abstract class, but that’s more a design issue than a code issue. You can probably come up with arguments for either side, using … Read more
They are abstract classes/methods and need to be overridden. You can choose to override the functionality or just let it do what the parent classs is doing. An abstract class is a class that is declared abstract—it may or may not include abstract methods. Abstract classes cannot be instantiated, but they can be subclassed. An … Read more
class X { }; class Y : public X { public: // For defining an abstract class without pure virtual functions: virtual ~Y() = 0; virtual void method() = 0; }; class Z : public Y { public: void method() override { } }; 7 solved C++ class declarations (inheritence) [closed]