In one of my interviews, I have been asked to explain the difference between an Interface and an Abstract class. Here’s my response: Methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behaviour. Variables declared in a Java interface are … Read more
What is the difference between abstract class and interface in Python? 8 s 8 What you’ll see sometimes is the following: class Abstract1: “””Some description that tells you it’s abstract, often listing the methods you’re expected to supply.””” def aMethod(self): raise NotImplementedError(“Should have implemented this”) Because Python doesn’t have (and doesn’t need) a formal Interface … Read more
Java 8 allows for default implementation of methods in interfaces called Default Methods. I am confused between when would I use that sort of interface default method, instead of an abstract class (with abstract method(s)). So when should interface with default methods be used and when should an abstract class (with abstract method(s)) be used? … Read more
The question is in Java why can’t I define an abstract static method? for example abstract class foo { abstract void bar( ); // <– this is ok abstract static void bar2(); //<– this isn’t why? } 29 s 29 Poor language design. It would be much more effective to call directly a static abstract … Read more
Can an abstract class have a constructor? If so, how can it be used and for what purposes? 22 s 22 Yes, an abstract class can have a constructor. Consider this: abstract class Product { int multiplyBy; public Product( int multiplyBy ) { this.multiplyBy = multiplyBy; } public int mutiply(int val) { return multiplyBy * … Read more
How do I setup a class that represents an interface? Is this just an abstract base class? 17 s 17 To expand on the answer by bradtgmurray, you may want to make one exception to the pure virtual method list of your interface by adding a virtual destructor. This allows you to pass pointer ownership … Read more
I have had recently two telephone interviews where I’ve been asked about the differences between an Interface and an Abstract class. I have explained every aspect of them I could think of, but it seems they are waiting for me to mention something specific, and I don’t know what it is. From my experience I … Read more
What exactly is the difference between an interface and an abstract class? 3 38
Yes, an abstract class can have a constructor. Consider this: abstract class Product { int multiplyBy; public Product( int multiplyBy ) { this.multiplyBy = multiplyBy; } public int mutiply(int val) { return multiplyBy * val; } } class TimesTwo extends Product { public TimesTwo() { super(2); } } class TimesWhat extends Product { public TimesWhat(int … Read more
Class ‘Room’ is abstract; cannot be instantiated
