I am interating through classes in a Jar file and wish to find those which are not abstract. I can solve this by instantiating the classes and trapping InstantiationException but that has a performance hit as some classes have heavy startup. I can’t find anything obviously like isAbstract() in the Class.java docs. 3 Answers 3
Consider an example (which compiles in java) public abstract interface Interface { public void interfacing(); public abstract boolean interfacing(boolean really); } Why is it necessary for an interface to be “declared” abstract? Is there other rules that applies with an abstract interface? Finally: If abstract is obsolete, why is it included in Java? Is there … Read more
This question already has answers here: Is it possible to make abstract classes in Python? (13 answers) Closed 3 years ago. I am having trouble in using inheritance with Python. While the concept seems too easy for me in Java yet up till now I have been unable to understand in Python which is surprising … Read more
Data classes seem to be the replacement to the old-fashioned POJOs in Java. It is quite expectable that these classes would allow for inheritance, but I can see no convenient way to extend a data class. What I need is something like this: open data class Resource (var id: Long = 0, var location: String … Read more
How can I make a class or method abstract in Python? I tried redefining __new__() like so: class F: def __new__(cls): raise Exception(“Unable to create an instance of abstract class %s” %cls) but now if I create a class G that inherits from F like so: class G(F): pass then I can’t instantiate G either, … Read more
During one of my interview, I was asked “If we can instantiate an abstract class?” My reply was “No. we can’t”. But, interviewer told me “Wrong, we can.” I argued a bit on this. Then he told me to try this myself at home. abstract class my { public void mymethod() { System.out.print(“Abstract”); } } … Read more
What is the difference between an abstract method and a virtual method? In which cases is it recommended to use abstract or virtual methods? Which one is the best approach? 2 28 An abstract function cannot have functionality. You’re basically saying, any child class MUST give their own version of this method, however it’s too … Read more
How to reproduce that error as simply as possible: Java code: package javaapplication3; public class JavaApplication3 { public static void main(String[] args) { } } class Cat implements Animal{ } interface Animal{ abstract boolean roar(); } Shows this compile time error: Cat is not abstract and does not override abstract method roar() in Animal Why … Read more