Can an abstract class 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.

Is abstract class always public?

Abstract Classes Compared to Interfaces

With interfaces, all fields are automatically public, static, and final, and all methods that you declare or define (as default methods) are public. In addition, you can extend only one class, whether or not it is abstract, whereas you can implement any number of interfaces.

Does abstract method have to be public?

abstract methods have the same visibility rules as normal methods, except that they cannot be private .

Can abstract class have non abstract private 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.

Can abstract class be protected?

And it can't be "some of them," since we would need a way of defining which classes can access it, which is what the visibility modifier was for in the first place. So for these reasons, top-level classes cannot be private or protected; they must be package-private or public.

Java Tutorials | Why Abstract Method cannot be declared with Private? by DURGA Sir

Can abstract class have final private modifiers?

A Java class containing an abstract class must be declared as abstract class. An abstract method can only set a visibility modifier, one of public or protected. That is, an abstract method cannot add static or final modifier to the declaration.

Can we declare interface methods as private?

Java 9 onwards, you can include private methods in interfaces. Before Java 9 it was not possible. In Java SE 7 or earlier versions, an interface can have only two things i.e. Constant variables and Abstract methods. These interface methods MUST be implemented by classes which choose to implement the interface.

What is the difference between abstract class & abstract method?

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. The body is provided by the subclass (inherited from).

What is the difference between interface and abstract class?

Abstract class can be inherited using extends keyword. Interface can only be implemented using implements keyword. Abstract class can have any type of members like private, public. Interface can only have public members.

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 abstract classes be instantiated?

Instantiation: An abstract class cannot be instantiated directly, i.e. object of such class cannot be created directly using new keyword. An abstract class can be instantiated either by a concrete subclass or by defining all the abstract method along with the new statement.

What is purpose of abstract class?

The purpose of an abstract class is to provide a blueprint for derived classes and set some rules what the derived classes must implement when they inherit an abstract class. We can use an abstract class as a base class and all derived classes must implement abstract definitions.

Can we inherit abstract class in Java?

If a class is declared abstract, it cannot be instantiated. To use an abstract class, you have to inherit it from another class, provide implementations to the abstract methods in it. If you inherit an abstract class, you have to provide implementations to all the abstract methods in it.

Can we have constructor in interface?

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 abstract class have static methods in Java?

If you declare a method in a class abstract to use it, you must override this method in the subclass. But, overriding is not possible with static methods. Therefore, an abstract method cannot be static.

Can we extend abstract class?

In Java, abstract means that the class can still be extended by other classes but that it can never be instantiated (turned into an object).

Can abstract class inherit from concrete class?

No. Abstract class can have both an abstract as well as concrete methods. A concrete class can only have concrete methods.

Can interface be instantiated?

An interface can't be instantiated directly. Its members are implemented by any class or struct that implements the interface. A class or struct can implement multiple interfaces.

Why is private not used in interfaces?

It is because they would be useless. There would be no way to call a private method. Private members are an implementation detail. An interface is about the public role that a class can take on.

Can we inherit private method in Java?

No, we cannot override private or static methods in Java. Private methods in Java are not visible to any other class which limits their scope to the class in which they are declared.

CAN interface have private members?

Therefore, the members of an interface cannot be private. If you try to declare the members of an interface private, a compile-time error is generated saying “modifier private not allowed here”.

Can we declare local inner class as abstract?

Yes, we can declare local inner class as abstract.

Can abstract class have final methods?

As a final class cannot be inherited. However, an abstract class can have a final method. This final method is treated like a normal method with a body which cannot be overridden.

Are all methods in an abstract class public?

It depends on your use case. If you want the methods of the abstract class visible to instances of your derived class, you should make them public. If, on the other hand, you want the methods visible only to your derived class, you should make them protected.

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.