Eclipse is defaulting to Java 1.5 and you have classes implementing interface methods (which in Java 1.6 can be annotated with @Override, but in Java 1.5 can only be applied to methods overriding a superclass method). Go to your project/IDE preferences and set the Java compiler level to 1.6 and also make sure you select … Read more
In line with the other answers, there are multiple ways to call super class methods (including the constructor), however in Python-3.x the process has been simplified: Python-3.x class A(object): def __init__(self): print(“world”) class B(A): def __init__(self): print(“hello”) super().__init__() Python-2.x In python 2.x, you have to call the slightly more verbose version super(<containing classname>, self), which … Read more
It violates encapsulation. You shouldn’t be able to bypass the parent class’s behaviour. It makes sense to sometimes be able to bypass your own class’s behaviour (particularly from within the same method) but not your parent’s. For example, suppose we have a base “collection of items”, a subclass representing “a collection of red items” and … Read more
Polymorphism is enforced dynamically (at runtime) based on the actual type of the object that is calling the method. It relies on the ability to assign an object of a subclass to a reference of the superclass. Also, notice that when you have an instance method in a class and you call another method inside … Read more