- 1 What is the use of abstract method in Java?
- 2 How do you write an abstract method?
- 3 Why use an abstract method?
- 4 What are abstract classes and methods?
- 5 Can abstract method have body?
- 6 What is the use of abstract class?
- 7 What is difference between abstract method and interface?
- 8 Can abstract class be empty?
- 9 Can abstract class have constructors?
- 10 Can we override the abstract method?
- 11 Can abstract method be private?
- 12 Can abstract class have normal methods?
- 13 How do you implement an abstract class?
What is the use of abstract method in Java?
The abstract keyword is a non-access modifier, used for classes and methods: Abstract class: is a restricted class that cannot be used to create objects (to access it, it must be inherited from another class). Abstract method: can only be used in an abstract class, and it does not have a body.
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.
What are abstract classes and methods?
Abstract classes are similar to interfaces. You cannot instantiate them, and they may contain a mix of methods declared with or without an implementation. However, with abstract classes, you can declare fields that are not static and final, and define public, protected, and private concrete methods.
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 the use of abstract class?
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.
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 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.
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 the abstract method?
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 abstract class have normal methods?
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.
How do you implement an abstract class?
To create an abstract class, just use the abstract keyword before the class keyword, in the class declaration. You can observe that except abstract methods the Employee class is same as normal class in Java. The class is now abstract, but it still has three fields, seven methods, and one constructor.