Is it necessary to implement all the methods of abstract classes in derived class?

Answer 1

An Abstract class is a way to organize inheritance, sometimes it makes no since to implement every method in a class (i.e. a predator class), it may implement some to pass to its children but some methods cannot be implemented without knowing what the class will do (i.e. eat() in a Tiger class). Therefore, abstract classes are templates for future specific classes.

A disadvantage is that abstract classes cannot be instantiated, but most of the time it is logical not to create a object of an abstract class. heloooooo

Answer 2

An abstract method is a method that is declared without an implementation (without braces, and followed by a semicolon), like this: abstract void add(double X, double Y);

If a class includes abstract methods, the class itself must be declared abstract

Answer 3

Abstract classes are generally used where you want an amount of behavior to be used by the class that extends the abstract class while at the same time giving options to the child class to provide a certain amount of behavior itself.

Answer 4

An abstract class is a base class for other classes that share similar functionality, but is itself an incomplete class and therefore cannot be instantiated. This might be desirable when you need a stable API for others to build classes upon, or when you have several specialized objects that all share a common base design that must be followed.

As a trivial example, you might have a Fruit class, an Apple class, and a Banana class. Both Apples and Bananas are Fruits, and each share similar aspects, as well as unique aspects. However, you never want to instantiate a Fruit, as it must always be an Apple or a Banana. By declaring the class as "abstract", you can create a Fruit variable that can hold either an Apple or a Banana. You can freely call functions common to both (calling possibly different function bodies). You may also cast the Fruit into an Apple or Banana context if you need to access special functions or properties that are unique to that Fruit.

This allows you to create compact code by using a common, reusable class that in itself should never be created, but is intended to be a framework or guideline of other classes that should follow its pattern.

Answer 5

Abstract methods are very important in java in cases wherein you want to enforce certain standard behavior in your class and all classes that implement your class and at the same time, have the flexibility of allowing the programmer who is using your class as a parent class in his own code to provide custom implementation for certain behaviors.

Answer 6

Yes - It is Necessary to implement all methods of the abstract class in your class - If you want a concrete class that can be instantiated. If you dont plan on implementing all methods, then you have to declare your current class too as Abstract.

Abstract classes are generally used where you want an amount of behaviour to be used by the class that extends the abstract class while at the same time giving options to the child class to provide a certain amount of behaviour itself.

Answer 7

An abstract method is one that only has a declaration but no definition. An abstract method is usually part of an abstract class.

You would typically want to define an abstract class when you want to create an outline of what you want your child classes to do/implement. But, at the same time want to ensure that certain functionality of all your child classes is defined by you. An Abstract class can have both method definitions as well as implementations. So, both of the above can be done in an abstract class. Whereas, an Interface can only have method declarations with no definitions.

Answer 8

An abstract method is a method, in object-oriented software, of an abstract class which has to be implemented by all subtyping classes.

Answer 9

This has to do with inheritance. An abstract method ensures that all inherited classes have such a method.