what is difference between concrete class and abstract class?
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The only real difference is that a concrete class can be instantiated because it provides (or inherits) the implementation for all of its methods. An abstract class cannot be instantiated because at least one method has not been implemented. Abstract classes are meant to be extended.
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Concrete methods in interfaces The simplest form of this feature is the ability to declare a concrete method in an interface, which is a method with a body. A class that implements this interface need not implement its concrete method.
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An abstract class may contain non-final variables. Type of variables: Abstract class can have final, non-final, static and non-static variables. ... Multiple implementation: An interface can extend another Java interface only, an abstract class can extend another Java class and implement multiple Java interfaces.
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An abstract class can provide an implementation, i.e. (public, protected, private) method bodies. An interface can just declare public method signatures. ... Subclasses can only extend at most one abstract class, but can implement any number of interfaces.
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The main difference is the compiler won't let you instantiate an abstract class, while you could instantiate a base class (which may not make sense). Notice with the variable d we are guaranteed that the abstract methods have been overridden (otherwise the DerivedType class would have a compiler error).
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An abstract class can have an abstract method without body and it can have methods with implementation also. ... An abstract class is mostly used to provide a base for subclasses to extend and implement the abstract methods and override or use the implemented methods in abstract class.
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The main difference between the two is that with the Abstract Factory pattern, a class delegates the responsibility of object instantiation to another object via composition whereas the Factory Method pattern uses inheritance and relies on a subclass to handle the desired object instantiation.
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An abstract class cannot be instantiated directly, i.e. the object of such class cannot be created directly using the new keyword. ... An abstract method is declared by abstract keyword, such methods cannot have a body. If a class contains an abstract method, then it also needs to be abstract.
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The main difference between abstract class and final class in Java is that abstract class is a class with abstract and non-abstract methods and allows accomplishing abstraction, while final class is a class that restricts the other classes from accessing its data and methods.
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Answer: Yes, an abstract class can have a constructor, even though abstract class cannot be instantiated. An abstract class constructor c# code example will be explained. ... So, we need a constructor in abstract class to initialize database libraries.
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Yes, Abstract Classes can have constructors ! Abstract class can have a constructor though it cannot be instantiated. But the constructor defined in an abstract class can be used for instantiation of concrete class of this abstract class.
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Concrete class in Java. A concrete class is a class that has an implementation for all of its methods. They cannot have any unimplemented methods. It can also extend an abstract class or implement an interface as long as it implements all their methods. It is a complete class and can be instantiated.
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Concrete and abstract nouns are both "real," but one is a physical presence and the other is not. Concrete nouns represent things that can be experienced through the five senses. Abstract nouns refer to ideas and concepts that cannot be sensed on a physical level.
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Abstract class can define constructor. They are more structured and can have a state associated with them. While in contrast, default method can be implemented only in the terms of invoking other interface methods, with no reference to a particular implementation's state.
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A Java class can implement multiple interfaces but it can extend only one abstract class. 7. Interface is absolutely abstract and cannot be instantiated; A Java abstract class also cannot be instantiated, but can be invoked if a main() exists.
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The Class is the collection of the similar kind of objects whereas an object is the instantiation of a class. The objects are said to be the physical entity used in a program for some specific purpose. On the other hand, the class is considered a logical entity used to bind data and functions.
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The abstract keyword enables you to create classes and class members that are incomplete and must be implemented in a derived class. The sealed keyword enables you to prevent the inheritance of a class or certain class members that were previously marked virtual.