A final class cannot have any subclasses. An abstract class cannot be instantiated unless it is extended by a subclass.
Differences:Abstract class can also contain method definitions but an interface can contain only declarationsAll variables in an interface are by default public static and final whereas in Abstract class it is notAn interface can be considered as a pure abstract class that contains no method implementations and contains only declarations.
No. The abstract keyword means that you cannot instantiate the class unless you extend it with a subclass. The final keyword means that you cannot create subclasses of that class.Combining them would lead to an unusable class, so the compiler will not let this happen.
We can't instantiate both interfaces and abstract classes.The only one difference between them is that an interface can't contain concrete(fully defined) methods where as an abstract class may contain them.An abstract class not necessarily contain abstract methods. we can make a class as abstract class even it does not has any abstract methods.When there is a need to write both abstract and concrete methods in a single unit we have to use an abstract class instead of an interface since an interface cant contain concrete methods.All the fields(or properties) of an interface are by default 'static final' even when you don't mention explicitly. And all methods are 'public abstract'.But in an abstract class we can have any type of fields and methods.
final is a keyword.it can be used for three posibilities. they are ->we can assign the variable as final. to declaring the variable as final to avoid the reusability of a variable. now i display small program for this type. class A { final int i=10; a(int b) { i=b; System.out.println(i); } } public static void main(String args[]) { A x=new A(20); } } to execute this program .we have an error message.i.e.,the variable i can not be override. ->to use method have final keyword it can not be override.and also ->to use classes has final they can not be inhereted to sub classes.
Yes. You cannot inherit a final class but very well instantiate a final class
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Yes, a class can be defined as final and abstract also.
Differences:Abstract class can also contain method definitions but an interface can contain only declarationsAll variables in an interface are by default public static and final whereas in Abstract class it is notAn interface can be considered as a pure abstract class that contains no method implementations and contains only declarations.
No. The abstract keyword means that you cannot instantiate the class unless you extend it with a subclass. The final keyword means that you cannot create subclasses of that class.Combining them would lead to an unusable class, so the compiler will not let this happen.
We can't instantiate both interfaces and abstract classes.The only one difference between them is that an interface can't contain concrete(fully defined) methods where as an abstract class may contain them.An abstract class not necessarily contain abstract methods. we can make a class as abstract class even it does not has any abstract methods.When there is a need to write both abstract and concrete methods in a single unit we have to use an abstract class instead of an interface since an interface cant contain concrete methods.All the fields(or properties) of an interface are by default 'static final' even when you don't mention explicitly. And all methods are 'public abstract'.But in an abstract class we can have any type of fields and methods.
final is a keyword.it can be used for three posibilities. they are ->we can assign the variable as final. to declaring the variable as final to avoid the reusability of a variable. now i display small program for this type. class A { final int i=10; a(int b) { i=b; System.out.println(i); } } public static void main(String args[]) { A x=new A(20); } } to execute this program .we have an error message.i.e.,the variable i can not be override. ->to use method have final keyword it can not be override.and also ->to use classes has final they can not be inhereted to sub classes.
Yes. You cannot inherit a final class but very well instantiate a final class
® {} class [extends class_name] [implements {, }] ® public | abstract | final ® {} class [extends class_name] [implements {, }] ® public | abstract | final
They are very different. An abstract class is a class that represents an abstract concept (google define "abstract" if you're unsure) such as 'Thoughts' or 'BankAccount'. When a class is defined as abstract it cannot be used (directly) to create an object. Abstract classes are used as super-classes so that all of their subclasses inherit all methods. Interfaces can be thought of as contracts with all of their implementing classes. They simply require all implementing classes to have methods with the same signature as that defined in the interface, but such methods can behave as appropriate. Hope that helps :)
Abstract classes are to be extended until to a concrete class.Can have both abstract & non abstract methods.An Abstract class can not be instantiated.A non abstract class can be extended to an abstract class.If At least one abstract method present in a class then that class must be abstract.abstract & final modifiers can never be together.abstract classes can have both abstract methods & non abstract methods.
Comparison between an Abstract Class and an Interface:While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict:
Because of the following reasons:static - If a constructor is static, an object instance cannot invoke it to initialize itself (Because static members are not linked to an object)abstract - because an abstract class cannot be instantiated and hence it will not have a constructor. If you make a concrete class's constructor abstract - it cannot be instantiated. eitherways it makes no sensefinal - a constructor cannot be final (thats the way java is designed)