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What are the differences between class and abstract class?
Below is the main difference between the 3 components:Concrete class - Provides implementation for all its methods & also for methods from extended abstract classes or implemented interfacesAbstract class - Does not provide implementation for one or more of its methodsInterface - Does not provide implementation for any of its methods
Abstract class can be private?
A class can either be default or public it can never be declared as private, so the question of abstract class at the file level does not arise. But an inner class can be declared private and abstract as well.
How constructor called?
You cannot invoke a constructor explicitly. It will get invoked implicitly when you call the new keyword on the class to create an object of the class. Ex: private ClassExample obj = new ClassExample(); here this new keyword usage on the ClassExample class will invoke the constructor of this class and create an object of that class.
What is purpose of abstraction in java?
Abstract keyword used for method declaration declares the methods without implementations. Abstract class in java have abstract methods that is not implemented in abstract class, but implemented in subclasses in java program. If the class in java program is not required to get instantiated than that class use the abstract keyword but this class rather is available for other classes to extend by other classes. Abstract keyword will be used in method declaration to declare that method without providing the implementation in that java program. In other words we can say that, it formally unfinished class as well as method, that marked with the help of keyword abstract. Defining abstract is a way of preventing someone from instantiating a class that is supposed to be extended first. In java program abstract class is deliberately missing similar to like an interface which will missing all method bodies in the program. Abstract class provides a way to extend an actual class. We will not use new on abstract classes but will use abstract references in the java program, that always point to objects of the class that extends an abstract class. In java program for practical use of an abstract class, we will define a non-abstract class that extends an abstract one. This will use any of the inherited non-abstract methods. Most of the time abstract class may extend another abstract class. In that condition it need not implement all in the non-abstract methods. An abstract keyword used both on classes and methods. In case of class declared with an abstract keyword may not be instantiated that is the only thing that abstract keyword doing.
Is it necessary to implement all the methods of abstract classes in derived class?
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
What are the differences between class and abstract class?
Below is the main difference between the 3 components:Concrete class - Provides implementation for all its methods & also for methods from extended abstract classes or implemented interfacesAbstract class - Does not provide implementation for one or more of its methodsInterface - Does not provide implementation for any of its methods
What is the purpose of declaring abstract method?
Abstract Class: The class which contains the common features of components of several classes, but cannot it be instantiated by itself. It represents an abstract concept for which there is no actual existing expression. For instance, "Vegetation" is an abstract class - there is no such real, real thing as generic vegetation. Instead, there are only instances of vegetation, such as mango tree and rose plant, which are types of vegetation, and share common characteristics, such as having leaves and stem in at least part of the lifecycle. SO in software engineering, an abstract class is a class in a nominative type system which is declared by the programmer, and which has the property that it contains members which are also members of some declared subtype. In many object oriented programming languages, abstract classes are known as abstract base classes, interfaces, traits, mixins, flavors, or roles. Note that these names refer to different language constructs which are (or may be) used to implement abstract types. We can also say that abstract class is : -- A class which is used only as an ancestor and is never instantiated. In other word a concrete definition will say that A type of class with pure virtual member functions and one or more methods that are declared but not implemented, that behaves as a base class but prohibits the instantiation of any members of that class. i.e. It has a complete interface but only a partial implementation It is used to take advantage of inheritance yet prohibiting the generation of objects that are not completely defined. Concrete subclasses of an abstract class are required to flesh out the implementation by overriding the abstract methods.
Abstract class can be private?
A class can either be default or public it can never be declared as private, so the question of abstract class at the file level does not arise. But an inner class can be declared private and abstract as well.
How constructor called?
You cannot invoke a constructor explicitly. It will get invoked implicitly when you call the new keyword on the class to create an object of the class. Ex: private ClassExample obj = new ClassExample(); here this new keyword usage on the ClassExample class will invoke the constructor of this class and create an object of that class.
What is purpose of abstraction in java?
Abstract keyword used for method declaration declares the methods without implementations. Abstract class in java have abstract methods that is not implemented in abstract class, but implemented in subclasses in java program. If the class in java program is not required to get instantiated than that class use the abstract keyword but this class rather is available for other classes to extend by other classes. Abstract keyword will be used in method declaration to declare that method without providing the implementation in that java program. In other words we can say that, it formally unfinished class as well as method, that marked with the help of keyword abstract. Defining abstract is a way of preventing someone from instantiating a class that is supposed to be extended first. In java program abstract class is deliberately missing similar to like an interface which will missing all method bodies in the program. Abstract class provides a way to extend an actual class. We will not use new on abstract classes but will use abstract references in the java program, that always point to objects of the class that extends an abstract class. In java program for practical use of an abstract class, we will define a non-abstract class that extends an abstract one. This will use any of the inherited non-abstract methods. Most of the time abstract class may extend another abstract class. In that condition it need not implement all in the non-abstract methods. An abstract keyword used both on classes and methods. In case of class declared with an abstract keyword may not be instantiated that is the only thing that abstract keyword doing.
Is it necessary to implement all the methods of abstract classes in derived class?
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
What is similarities between Abstract Class and Interface?
If a class has one abstract method ,the class has to be an abstract class.Methods can be implemented in abstract class.Whereas a interface is like a abstract class...the only difference being that the methods are never implemented in Interface.
What can be declared in an abstract class?
Abstract classes are to be extended until to a concrete class.Can have both abstract & non abstract methods.An Abstract class can not be instantiated.A non abstract class can be extended to an abstract class.If At least one abstract method present in a class then that class must be abstract.abstract & final modifiers can never be together.abstract classes can have both abstract methods & non abstract methods.
Why method inner classes can only access final variables from method?
I think the main reason is because the inner class may "outlive" the method in which it was created. If this happens, then the memory storing those variables would be lost and we would run into problems when trying to access them. If the variables are defined as final, then Java knows that those values will never change and it can move/copy them when the class is created.
Is never an abstract noun?
Yes, "never" is considered an abstract noun because it refers to the concept of time in a negative sense, indicating the absence of occurrence or existence. Unlike concrete nouns, which denote tangible objects or entities, "never" embodies an idea or experience rather than something that can be physically touched or seen.
Real time example for interface vs abstract class in java?
w.frnds........ I am just trying to an example of abstract class and interface class in real life . As these two ["interface class" is not a term in Java programming - just "interface"] classes [sic] are a concept of objest orientation so easy we can easily compare thhese with our real life . Suppose we have an abstract class called clark and an abstract method behabour of this abstract class ,which has no definition in abstract class. two other class security and receptionist inherits these clark class. So in thses two derived class there must has to be a defonation of behabour method,which depends on the derived class which types of behabour they will show........ So that is a real life example of Abstract class .Interface is also same as abstract class only the difference is it can't contain any implementation of any method in base class or super class. I think this is a sufficient example to understand abstract class and interface. [No, it is not sufficient.] If u have any doubt then u can contact me with this email id-rkmahanta26@gmail.com [Interfaces support multiple inheritance; classes do not. Interfaces contain only public members; classes do not have to. Interfaces do not have superclasses, except the implicit 'Object' supertype; they have superinterfaces. Nested interfaces are always static, never inner, unlike classes which can be inner classes. "u" is not an English pronoun. Use the tutorial and the JLS to understand interfaces and abstract classes, not this garbage answer.]
All things that never move?
Concepts such as ideas and principles that remain constant, static objects like rocks and mountains, and abstract notions like truth or numbers are examples of things that never move.
