A metaclass is the class of a class. A class defines how an instance of the class (i.e. an object) behaves while a metaclass defines how a class behaves. A class is an instance of a metaclass. While in Python you can use arbitrary callables for metaclasses (like Jerub shows), the better approach is to make it … Read more
What is the precise difference between encapsulation and abstraction?
Virtual methods have an implementation and provide the derived classes with the option of overriding it. Abstract methods do not provide an implementation and force the derived classes to override the method. So, abstract methods have no actual code in them, and subclasses HAVE TO override the method. Virtual methods can have code, which is … Read more
C++ is usually considered a “multi-paradigm” language. That is, you can use it for object-oriented, procedural, and even functional programming. Those who would deny that C++ is OO generally have beef with the fact that the primitive types are not objects themselves. By this standard, Java would also not be considered OO. It is certainly … Read more
In your method setDetails you haven’t specified anything for the return type, if it is not returning anything then specify void For Voter class for Candidates class One other thing, (Thanks to Frank Pavageau) your class name is Candidates and you have defined the constructor with Candidate without s, that is why it is being considered as a normal method, and thus should have a return type. You your rename … Read more
On a Java OOP project I got three errors on my constructor: .\Voter.java:14: error: invalid method declaration; return type required .\Candidates.java:7: error: invalid method declaration; return type required .\Candidates.java:14: error: invalid method declaration; return type required codes for constructor: i declared my constructors like this: Anything I missed?
If you think about the Greek roots of the term, it should become obvious. Poly = many: polygon = many-sided, polystyrene = many styrenes (a), polyglot = many languages, and so on. Morph = change or form: morphology = study of biological form, Morpheus = the Greek god of dreams able to take any form. So … Read more
Variables declared inside the class definition, but not inside a method are class or static variables: As @millerdev points out, this creates a class-level i variable, but this is distinct from any instance-level i variable, so you could have This is different from C++ and Java, but not so different from C#, where a static member can’t be accessed using … Read more
What the inFile >> S does is take in the file stream, which is the data in you file, and uses a space delimiter (breaks it up by whitespace) and puts the contents in the variable S. For example: If we had a file that had the follow contents and we used inFile >> S with our file: we … Read more
As mentioned by other here: Interfaces are not necessary in Python. This is because Python has proper multiple inheritance, and also ducktyping, which means that the places where you must have interfaces in Java, you don’t have to have them in Python. That said, there are still several uses for interfaces. Some of them are covered by … Read more