- Can main method be abstract?
- What is difference between abstract and interface?
- Is interface an abstract class?
- Can a final class be abstract?
- How do you write a method abstract?
- Can abstract class have constructor?
- Are all methods in an abstract class abstract?
- Can a method be both private and abstract?
- Can abstract class have static methods?
- Can we override static method?
- Can we use final keyword in abstract class?
- Can abstract class have normal methods?
- Which is better abstract class or interface?
- What are abstract methods?
- When should we use abstract class?
Can main method be abstract?
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.
The abstract is applicable to the object so there is no problem if it contains the main method..
What is difference between abstract and interface?
Classes can implement multiple interfaces, but only one abstract class. Abstract classes can contain non-abstract methods. They can both have methods, variables, and neither one can be instantiated. All variables declared in an interface are final, while an abstract class may contain non-final variables.
Is interface an abstract class?
An interface is abstract so that it can’t provide any code. An abstract class can give complete, default code which should be overridden. You cannot use access modifiers for the method, properties, etc. You can use an abstract class which contains access modifiers.
Can a final class be abstract?
Since you cannot make a final class abstract in Java, this becomes illegal and compiler prohibits you from doing that by throwing an error. But, yes, you can declare static methods on both final class as well as abstract classes, there is no problem with that.
How do you write a method abstract?
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.
Can abstract class have constructor?
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.
Are all methods in an abstract class abstract?
Not all methods in an abstract class have to be abstract methods. An abstract class can have a mixture of abstract and non-abstract methods. Subclasses of an abstract class must implement (override) all abstract methods of its abstract superclass.
Can a method be both private and abstract?
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 static methods?
Can an abstract class have static methods? Yes, abstract class can have Static Methods. The reason for this is Static methods do not work on the instance of the class, they are directly associated with the class itself.
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’.
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 abstract class have normal methods?
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. … An abstract class can not be instantiated, which means you are not allowed to create an object of it.
Which is better abstract class or 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.
What are abstract methods?
An abstract method is a method that is declared without an implementation (without braces, and followed by a semicolon), like this: abstract void moveTo(double deltaX, double deltaY);
When should we use abstract class?
When to use an abstract classAn abstract class is a good choice if we are using the inheritance concept since it provides a common base class implementation to derived classes.An abstract class is also good if we want to declare non-public members. … If we want to add new methods in the future, then an abstract class is a better choice.More items…•