Pytanie |
Odpowiedź |
can you create an object of an abstract class? rozpocznij naukę
|
|
|
|
|
why do we have abstract classes? rozpocznij naukę
|
|
An abstract class gives a way of grouping common members (data and methods) of its subclasses.
|
|
|
how do you declare an abstract class or method? rozpocznij naukę
|
|
with the key word abstract
|
|
|
Why using an abstract class and not an ordinary superclass? rozpocznij naukę
|
|
To force the subclasses to provide and implement certain methods.
|
|
|
what is a method signature? rozpocznij naukę
|
|
the method name and the number, type and order of its parameters. Return types and thrown exceptions are not considered to be a part of the method signature.
|
|
|
rozpocznij naukę
|
|
Polymorphism is the capability of a method to do different things based on the object that it is acting upon. In other words, polymorphism allows you define one interface and have multiple implementations
|
|
|
rozpocznij naukę
|
|
more than one method having the same name, if their argument lists are different.
|
|
|
rozpocznij naukę
|
|
Declaring a method in sub class which is already present in parent class is known as method overriding. Overriding is done so that a child class can give its own implementation to a method which is already provided by the parent class.
|
|
|
what is the advantage of overriding? rozpocznij naukę
|
|
The main advantage of method overriding is that the class can give its own specific implementation to a inherited method without even modifying the parent class code.
|
|
|
why is overriding an example of runtime time (or dynamic polymorphism)? rozpocznij naukę
|
|
When a parent class reference points to the child class object then the call to the overridden method is determined at runtime, because during method call which method(parent class or child class) is to be executed is determined by the type of object.
|
|
|
what is dynamic method dispatch? rozpocznij naukę
|
|
This process in which a call to the overridden method is resolved at runtime
|
|
|
what are the rules for overriding? rozpocznij naukę
|
|
Type signatures must match and access modifyers of the overriding method(subclass method) cannot be more restrictive
|
|
|
what are the 3 ways to overload a method? rozpocznij naukę
|
|
change Number of parameters, Data type of parameters, Sequence of Data type of parameters
|
|
|
why is Method overloading is an example of Static Polymorphism. rozpocznij naukę
|
|
because it happens at compile time
|
|
|
rozpocznij naukę
|
|
When a data type of smaller size is promoted to the data type of bigger size than this is called type promotion, for example: byte data type can be promoted to short, a short data type can be promoted to int, long, double etc.
|
|
|
why is type promotion relevant to overloading? rozpocznij naukę
|
|
it is very important to understand type promotion else you will think that the program will throw compilation error but in fact that program will run fine
|
|
|
what are bytes promotions? rozpocznij naukę
|
|
|
|
|
what are shorts promotions? rozpocznij naukę
|
|
|
|
|
what are ints promotions? rozpocznij naukę
|
|
|
|
|
what are floats promotions? rozpocznij naukę
|
|
|
|
|
what are longs promotions? rozpocznij naukę
|
|
|
|
|