- Why do we need interface?
- What is abstract class vs interface?
- Can abstract class have main method?
- Can we define abstract method as static?
- Can we override static method?
- What is difference between abstract class and interface?
- Can abstract class have private methods?
- What is difference between static and abstract class?
- Can we make abstract class as static in Java?
- Why we Cannot override static method?
- Can abstract class have constructors?
- Can abstract class be inherited?
- Can we write a static modifier in an abstract class?
- Can we use final keyword in abstract class?
- Can we have static method in interface?
Why do we need interface?
Why do we use interface .
It is used to achieve total abstraction.
Since java does not support multiple inheritance in case of class, but by using interface it can achieve multiple inheritance .
The reason is, abstract classes may contain non-final variables, whereas variables in interface are final, public and static..
What is abstract class vs interface?
The short answer: An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it. And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.
Can abstract class have main method?
Yes, you can use the main method in abstract class. The main method is a static method so it is associated with Class, not with object/ instance. … In main method, you can not create an instance of the abstract class but you can instantiate other concrete class.
Can we define abstract method as static?
Declaring abstract method static 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 override static method?
Can we Override static methods in java? We can declare static methods with the same signature in the subclass, but it is not considered overriding as there won’t be any run-time polymorphism. Hence the answer is ‘No’.
What is difference between abstract class and interface?
Abstract class and interface both are used to achieve abstraction where we can declare the abstract methods. Abstract class and interface both can’t be instantiated….Difference between abstract class and interface.Abstract classInterface7) An abstract class can be extended using keyword “extends”.An interface can be implemented using keyword “implements”.8 more rows
Can abstract class have private methods?
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.
What is difference between static and abstract class?
An abstract class is intended to be used as a base of a class inheritance hierarchy. A static class cannot be the base of a class inheritance hierarchy. A static class is intended for singleton state or stateless functionality.
Can we make abstract class as static in Java?
You cannot create an abstract static method. … 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.
Why we Cannot override static method?
Static methods cannot be overridden because they are not dispatched on the object instance at runtime. The compiler decides which method gets called. Static methods can be overloaded (meaning that you can have the same method name for several methods as long as they have different parameter types).
Can abstract class have constructors?
Yes! Abstract classes can have constructors! Yes, when we define a class to be an Abstract Class it cannot be instantiated but that does not mean an Abstract class cannot have a constructor. Each abstract class must have a concrete subclass which will implement the abstract methods of that abstract class.
Can abstract class be inherited?
An abstract class defines the identity of a class. An interface can inherit multiple interfaces but cannot inherit a class. An abstract class can inherit a class and multiple interfaces. … An abstract class can declare constructors and destructors.
Can we write a static modifier in an abstract class?
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 use final keyword in abstract class?
Yes, there may be “final” methods in “abstract” class. But, any “abstract” method in the class can’t be declared final. It will give “illegal combination of modifiers: abstract and final” error. Here is the working example of the implementation.
Can we have static method in interface?
Similar to Default Method in Interface, the static method in an interface can be defined in the interface, but cannot be overridden in Implementation Classes. To use a static method, Interface name should be instantiated with it, as it is a part of the Interface only.