Can abstract class have constructor?

Like any other classes in Java, abstract classes can have constructors even when they are only called from their concrete subclasses.

Can we have a constructor in abstract class?

Yes, an Abstract Class can have a Constructor. You Can Overload as many Constructor as you want in an Abstract Class. These Contractors Can be used to Initialized the initial state of the Objects Extending the Abstract Class.

Why does abstract class have constructor?

The main purpose of the constructor is to initialize the newly created object. In abstract class, we have an instance variable, abstract methods, and non-abstract methods. We need to initialize the non-abstract methods and instance variables, therefore abstract classes have a constructor.

Can abstract classes be final?

If you declare a class abstract, to use it, you must extend it and if you declare a class final you cannot extend it, since both contradict with each other you cannot declare a class both abstract and final if you do so a compile time error will be generated.

Can we override constructor?

Constructor looks like method but it is not. It does not have a return type and its name is same as the class name. But, a constructor cannot be overridden. If you try to write a super class's constructor in the sub class compiler treats it as a method and expects a return type and generates a compile time error.

Part 8 Can an abstract class have a constructor

Can interface class have constructor?

No, you cannot have a constructor within an interface in Java. You can have only public, static, final variables and, public, abstract, methods as of Java7. From Java8 onwards interfaces allow default methods and static methods. From Java9 onwards interfaces allow private and private static methods.

Can we declare private constructor in abstract class?

Answer: Yes. Constructors in Java can be private. All classes including abstract classes can have private constructors. Using private constructors we can prevent the class from being instantiated or we can limit the number of objects of that class.

Why there is no constructor in interface?

Constructor in an interface

An Interface in Java doesn't have a constructor because all data members in interfaces are public static final by default, they are constants (assign the values at the time of declaration). There are no data members in an interface to initialize them through the constructor.

Can an interface be final?

No ;Interface only have abstract methods. methods. interface method can not be final .

Can abstract class have static methods?

Yes, of course you can define the static method in abstract class. you can call that static method by using abstract class,or by using child class who extends the abstract class. Also you can able to call static method through child class instance/object.

Can we use super super in Java?

The super keyword in Java is a reference variable that is used to refer parent class objects. The super() in Java is a reference variable that is used to refer parent class constructors. super can be used to call parent class' variables and methods. super() can be used to call parent class' constructors only.

Can an abstract class have concrete methods?

Abstract class can have both an abstract as well as concrete methods. A concrete class can only have concrete methods. Even a single abstract method makes the class abstract.

Can we instantiate abstract class?

Abstract classes cannot be instantiated, but they can be subclassed. When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract .

Can abstract class have main () function defined inside it?

Can abstract class have main() function defined inside it? Explanation: This is a property of abstract class. It can define main() function inside it. There is no restriction on its definition and implementation.

Can I inherit static method from interfaces?

Static methods in interfaces are never inherited.

CAN interface have private methods?

An interface can have private methods since Java 9 version. These methods are visible only inside the class/interface, so it's recommended to use private methods for confidential code. That's the reason behind the addition of private methods in interfaces.

Can abstract class have non abstract methods?

Yes, we can declare an abstract class with no abstract methods in Java. An abstract class means that hiding the implementation and showing the function definition to the user. An abstract class having both abstract methods and non-abstract methods. For an abstract class, we are not able to create an object directly.

Can we declare a class as static?

So, Yes, you can declare a class static in Java, provided the class is inside a top-level class. Such clauses are also known as nested classes and they can be declared static, but if you are thinking to make a top-level class static in Java, then it's not allowed.

Can we declare abstract method as 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 create immutable class in Java?

In Java, when we create an object of an immutable class, we cannot change its value. For example, String is an immutable class. Hence, we cannot change the content of a string once created. Besides, we can also create our own custom immutable classes.

Can I override a method in an abstract class?

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 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 methods have a 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.

Can we override static method?

No, we cannot override static methods because method overriding is based on dynamic binding at runtime and the static methods are bonded using static binding at compile time. So, we cannot override static methods.

Is overriding possible in Java?

In Java, method overriding occurs when a subclass (child class) has the same method as the parent class. In other words, method overriding occurs when a subclass provides a particular implementation of a method declared by one of its parent classes.