What is the C# equivalent syntax for the following Java statement:
public class Lion extends Animal implements Diurnal()
{
}
Animal is Base class
Diurnal is an Interface
the inheritance could be declared like this.
public class Lion : Animal, Diurnal
{
}
In C#, you can inherit one base class and can be multiple Interfaces.
One more tip, if you are making an Interface in C#, prefix it with I. eg IDiurnal
public class Lion : Animal, // base class must go first
Diurnal // then interface(s) if any
{
}
Would look something like this:
public class Lion :Animal, Diurnal {
}
Where Animal is a class and Diurnal is an interface.
Please note, that according to the C# naming convention, interface has to have "I" infront of its name, so finally it should look like this:
public class Lion :Animal, IDiurnal {
}
In C#, there is uniform syntax for extending class and implementing interface.
public class Lion : Animal, Diurnal {
}
you need to write down first base class like(Animal is base class),
lately interfaces like as(Diurnal is a Interface)
public class Lion : Animal, Diurnal {}
the first name after : is the extended class, after comes the implemented interfaces
public class Lion : Animal, Diurnal
{
}
c# do not allow multiple class extension, but you can implement many interfaces
public class Lion : Animal, Diurnal
{
}
interface Diurnal
{
}
class Animal
{
}
Class Animal was inherited by Lion class. Diurnal class is interface.
Related
I am trying model a zoo.
Suppose I have the following structure for areas in the Zoo(omitted some details)
public abstract class AnimalHabitat{
private ArrayList<Animal> animals = new ArrayList<>();
public void setAnimal(Animal animal) {
animals.add(animal)
}
}
public class Enclosure extends AnimalHabitat{}
public class Aquarium extends AnimalHabitat{}
public class Cage extends AnimalHabitat{}
Then I have the following structure for animals
public abstract class Animal{}
public class Lion extends Animal{}
public class Zebra extends Animal{}
public class Shark extends Animal{}
public class Starfish extends Animal{}
public class Parrot extends Animal{}
public class Eagle extends Animal{}
I want to add an animal to its corresponding appropriate habitat. To simplify code I was thinking to use either a marker interface, such as
public interface TerrestrialAnimal{}
public class Lion extends Animal implements TerrestrialAnimal{}
public class Zebra extends Animal implements TerrestrialAnimal{}
and then I will be able to do
public class Zoo{
public boolean addAnimal(AnimalHabitat habitat, Animal animal) {
if (animal instanceOf TerrestrialAnimal && habitat instanceOf Enclosure) {
habitat.set(animal);
return true;
}
if (animal instanceOf AquaticAnimal && habitat instance of Aquarium) {
habitat.set(animal);
return true;
}
// So for aerial
}
}
However an alternative is to use enums. For example suppose I have
public enum AnimalType{
Terrestrial, Aquatic, Aerial;
//getter
}
Then in the Animal abstract class I can define
public abstract class Animal{
private AnimalType type;
// Initialise in the constructor depending on the animal instance
}
And I will do the same in the addAnimal() method in Zoo.
What are the pros and cons of each approach? Thanks!
I would use enums. You don't need all of those if statements.
Just have the attribute type in both Animal and AnimalHabitat and then compare them.
if (animal.getType() == habital.getType()) { // can add to habitat
Switch to interfaces if you want to add some methods to the interface specific to the animal type.
Enum
pros:
Easy to scale: You can easily add value
More coincise: You have one single file to define all AnimalType
More readable: definitely readable
More Flexible: You can define method on Enum and you can print AnimalType using enum value
Comparable: You can do simple compare instead of using instanceof
with enums approach i doesn't find any cons.
Interface
pros
Methods: You can define common methods signatures
You can use 2 interfaces in same Animal (may an animal have more habitat? Or more types?)
you can use interface as supertype in collections/class variable
cons
Expensive: definitely expensive, one interface for each type
In your example i prefer Enums because you are using interfaces to define animal types and it can be done easily using Enums. Use interfaces if you need to define common method signatures or you want to use Interfaces as supertype as follow:
List<TerrestrialAnimal> terrestrialAnimal = new ArrayList<>(); it can contains all terrestiral animal.
Can somebody explain (like for dummies) the following examples of inheritance in Java:
1) public class Dog <T extends Animal> {....
2) public class Buldog extends Dog<DogFood, DogCommands> {....
3) public class Buldog<T extends DogFood, K extends DogCommands> extends Animal implements LivingBeign, LivingThing<T,K> { ....
1) public class Dog <T extends Animal> {...
There will be an generic type In your Dog class which is inherit variables and methods from class (probably an abstract class Animal)
This T must have and animal property.. For example assume you have a class Mammalian. We know that all mammalian are animal so they have what all animals have, and they can what all animals can.
So yo can call this as
public Dog<Mammalian> myDog = ...
There is a different situation.
2) public class Buldog extends Dog<DogFood, DogCommands> {....
So your dog class should be written like
/** T refers the food, and K refers commands*/
public class Dog<T,K> {....
So when you want to extend your class with Bulldog, you can leave generic or specify those generic types..
3) public class Buldog<T extends DogFood, K extends DogCommands> extends Animal implements LivingBeign, LivingThing<T,K> { ....
This is also as easy as above codes. The difference that you are desiring subclass of DogFood, which can be anyting, it can be Pap or Milk or Meat, and some subclass of DogCommands for example SitCommand, PlayCommand.. And as you are creating Buldog you know that It is Animal, so you don't want to write animal's property and methods again and since in Java you can't multiple inherit, you want also the other interfaces methods in your class..
I hope it is more understandable now.
I have the abstract parent class Animal:
public abstract class Animal
{
public abstract <T extends Animal> T copyAnimal(T animal);
}
I then want to create a subclass Duck but to override the copyAnimal I want to use Duck as the parameters such that:
public class Duck extends Animal
{
#Override
public Duck copyAnimal(Duck duck)
{
return copyOfDuck;
}
}
This of course gives me a compiler error saying that the method is not overridden. That being said how can I adjust this code so that I don't have to pass Animal to the copyAnimal() method to save casting, etc. since it looks ugly and would require additional runtime checks. Or is it even possible? And if not then what's the most elegant solution?
public abstract class Animal<A extends Animal<A>>
{
public abstract A copyAnimal(A animal);
}
Then:
public class Duck extends Animal<Duck>
Note that you can't constrain it to be the "self" type (e.g. it could be Duck extends Animal<Pig>); you just have to only declare the classes you want to declare.
im new here...
i have a little question regarding OOP rules.
let's say we have 3 classes:Bird,Cat & dog.
for both dog and cat have a fourlegs() method, and all of them have an eat() mathod.
what is the best way to accomplish this task:
*create Animal class with eat(), create Pet class with fourlegs() which will inherit from Animal class.
after then,cat &dog classes inherit from Pet while bird only inherit from Animal.
*since that there are differenet mathods for several classes object-oriented is not relevant here.
thank you very much!
I think you almost answer your own question. Create a class-hierarchy with the "Animal"-interface as the top-node.
I made an example of the hierarchy here.
Also, inheritance and polymorphi is some of the essentials of OOP, so I don't get your last sentence.
You could make a interface / abstract class Animal. Bird, Cat and Dog inherit from Animal.
Since the number of legs is something that cannot be categorized by making them depend on Mammal, Pet or something else, I would define an interface FourLegged. This would also enable you to not bind fly() to bird... there are birds that can't fly and insects that can fly:
public abstract class Animal {}
public interface FourLegged {}
public interface Flyer {}
public class Dog extends Animal implements FourLegged {}
public class Bird extends Animal implements Flyer {}
It depends on your needs whether Animal is an interface or an abstract class.
You could use the following sample code:
Declare class Animal
class Animal(){
void eat(){
... do something ...
}
}
Declare class Pet
class Pet() extends Animal{
/* This class has inherited eat() method as declared in class Animal.
If you want to change it, you must use #Override. */
void fourlegs(){
... do something ...
}
}
Declare classes Dog and Cat
class Dog extends Pet{
/* This class has inherited both eat() and fourlegs() from class Pet. */
...
}
and the same for class Cat.
Declare class Bird
class Bird extends Animal{
/* This class has inherited eat() method as declared in class Animal.
...
}
OOP programming is certainly related to this exercise, as you need to use inheritance (which is one of OOP's characteristics) in order to accomplish it.
Currently, I have the following class design :
AnimalHandler (A base class for all animals)
TigerHandler extends AnimalHandler, LionHandler extends AnimalHandler, LeopardHandler extends AnimalHandler and so on.
TigerHandler, LionHandler, LeopardHandler etc "HAS A" Tiger, Lion, Leopard and so on.
Now the issue is : TigerHandler, LionHandler, LeopardHandler etc are all the same(they have the same methods, etc) except that they deal with Tiger,Lion, Leopard, etc classes respectively. So if I need a new Animal group called Cheetah, I just need to copy any of the (Tiger|Lion|Leopard)Handler and do a search and replace of its "HAS A" class names like Tiger,Lion, Leopard.
Instead of copying/creating a new CheetahHandler as above, is there a way (design) that I can use ? Like, say, a GenericHandler that can deal with any of these "HAS A" classes (like Tiger,Lion, Cheetah, etc).
If all your handlers do is provide type safety, and does nothing else, you can use generics instead:
public class AnimalHandler<T extends Animal> {
private T theAnimal;
public T getTheAnimal() {}
// Etc
}
Using generics is a much better approach.
Make sure all animal classes (Tiger, Lion, Leopard) extends lets say an Animal class.
Then use:
public class AnimalHandler<A extends Animal> {
private A animal;
}
And use animal inside your code.
When you want to instantiate a tiger handler, use it as:
AnimalHandler<Tiger> tigerHandler = new AnimalHandler<>();
A bit of details in terms of how each of Tiger,Lion, Leopard classes are used in each of the handler
-- If the method interfaces are all the same, and only internal functionality is different
-- if there is extension on Animalhandler you are doing inside the childHandlers
Then, then you should make AnimalHandler an abstract class (implementing iAnimalHandler) and use generics to process the Animal (Super class for each Tiger,Lion, Leopard )
As others have noted, generics are a great approach, or you could use a Strategy pattern:
class Animalhandler {
List<Animal> animals;
// add, remove and do stuff with animals
}
interface Animal {
void makeSound();
}
class Cat extends Animal {
public void makeSound() {
// meow
}
}