- 1 What is abstract method in Java with example?
- 2 How do you write an abstract method?
- 3 Why use an abstract method?
- 4 Why is abstract used in Java?
- 5 Can abstract method have body?
- 6 What is abstract class example?
- 7 Can abstract class be empty?
- 8 What is difference between abstract method and interface?
- 9 Can abstract class have constructors?
- 10 Can we override abstract method in Java?
- 11 Can abstract method be private?
- 12 Can we overload abstract method in Java?
- 13 Can we use Final in abstract class?
- 14 What are the features of an abstract class?
- 15 What is abstraction OOP?
What is abstract method in Java with example?
A method without body (no implementation) is known as abstract method. A method must always be declared in an abstract class, or in other words you can say that if a class has an abstract method, it should be declared abstract as well.
How do you write an abstract method?
To declare an abstract method, use this general form: abstract type method -name(parameter-list); As you can see, no method body is present. Any concrete class(i.e. class without abstract keyword) that extends an abstract class must override all the abstract methods of the class.
Why use an abstract method?
An abstract class captures common characteristics of subclasses and may or may not contain any abstract method. It cannot be instantiated but can be only used as a superclass by its subclasses. If an abstract class doesn’t have any method implementation, it’s always better to use interface.
Why is abstract used in Java?
Abstract classes cannot be instantiated and are designed to be subclassed. They are used to provide some common functionality across a set of related classes while also allowing default method implementations. In this article, we’ll discuss a real world scenario for using an abstract class in Java.
Can abstract method have body?
Abstract methods cannot have body. Abstract class can have static fields and static method, like other classes. An abstract class cannot be declared as final.
What is abstract class example?
A class that is declared using “ abstract ” keyword is known as abstract class. It can have abstract methods(methods without body) as well as concrete methods (regular methods with body). A normal class (non- abstract class ) cannot have abstract methods.
Can abstract class be empty?
A empty abstract class can be used to group together classes. This is in order to show some intent and to ensure the single responsibility principle that a class should have just one purpose. The example you give uses an interface, not an empty abstract class. You use packages for that.
What is difference between abstract method and interface?
An abstract method is one method. An abstract class can contain several methods, and so can an interface. The difference between those two is that an abstract class can have implementations for some of its methods, while an interface doesn’t have any implementations.
Can abstract class have constructors?
The constructor inside the abstract class can only be called during constructor chaining i.e. when we create an instance of sub- classes. This is also one of the reasons abstract class can have a constructor.
Can we override abstract method in Java?
We use the abstract keyword to create abstract classes and methods. An abstract method doesn’t have any implementation ( method body). A subclass must override all abstract methods of an abstract class. However, if the subclass is declared abstract, it’s not mandatory to override abstract methods.
Can abstract method be private?
If a method of a class is private, you cannot access it outside the current class, not even from the child classes of it. But, incase of an abstract method, you cannot use it from the same class, you need to override it from subclass and use. Therefore, the abstract method cannot be private.
Can we overload abstract method in Java?
Yes, you can have overloaded methods ( methods with the same name different parameters) in an interface. You can implement this interface and achieve method overloading through its methods.
Can we use Final in abstract class?
No, you cannot make an abstract class or method final in Java because the abstract and final are the mutually exclusive concept. An abstract method must be overridden to be useful and called but when you make the abstract method final it cannot be overridden in Java, hence there would be no way to use that method.
What are the features of an abstract class?
Abstract classes have the following features:
- An abstract class cannot be instantiated.
- An abstract class may contain abstract methods and accessors.
- It is not possible to modify an abstract class with the sealed modifier because the two modifiers have opposite meanings.
What is abstraction OOP?
Abstraction is the concept of object-oriented programming that “shows” only essential attributes and “hides” unnecessary information. The main purpose of abstraction is hiding the unnecessary details from the users. It helps in reducing programming complexity and efforts.