What is difference between concrete class and abstract class?

What is difference between concrete class and abstract class?

A concrete class can only have concrete methods. Even a single abstract method makes the class abstract. Abstract class can not be instantiated using new keyword. Abstract class can inherit another class using extends keyword and implement an interface.

What is a concrete type?

In programming languages, an abstract type is a type in a nominative type system that cannot be instantiated directly; a type that is not abstract – which can be instantiated – is called a concrete type.

What is abstract and concrete class?

An abstract class is meant to be used as the base class from which other classes are derived. The derived class is expected to provide implementations for the member functions that are not implemented in the base class. A derived class that implements all the missing functionality is called a concrete class .

What is a concrete sub class?

A concrete class is a subclass of an abstract class, which implements all its abstract method. If a class extends an abstract class, then it should define all the abstract methods (override) of the base abstract class. If not, the subclass(the class extending abstract class) must also be defined as abstract class.

How many types of concrete mix are there?

Different types of concrete grades and their uses

Concrete Grade Mix Ratio (cement : sand : aggregates) Compressive Strength
M7.5 1 : 4 : 8 7.5 MPa
M10 1 : 3 : 6 10 MPa
M15 1 : 2 : 4 15 MPa
M20 1 : 1.5 : 3 20 MPa

Can concrete class be a superclass?

A concrete class can have instances (objects) created of the Class, but abstract classes cannot have direct instances. If there are abstract classes, they must be superclasses. As an abstract class cannot have instances, the subclasses must be able to have instances to be useful.

Can an abstract class extend concrete?

An abstract class always extends a concrete class ( java. lang. Object at the very least). So it works the same as it always does.

Can abstract class have all concrete methods?

You can’t have an abstract method in a concrete class. If you want an abstract method, the class must also be abstract. Otherwise users could instantiate the class and try to implement its methods. However, if your class is abstract, it may have some methods that are abstract and others that are concrete.

How do we declare an abstract class?

You create an abstract class by declaring at least one pure virtual member function. That’s a virtual function declared by using the pure specifier ( = 0 ) syntax. Classes derived from the abstract class must implement the pure virtual function or they, too, are abstract classes.

Where do we use abstract class?

An 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. In an interface, all methods must be public.

Can abstract class have constructor C++?

A class with one (or more) virtual pure functions is abstract, and it can’t be used to create a new object, so it doesn’t have a constructor.

Can an interface have a constructor?

Constructor in an interface An Interface in Java doesn’t have a constructor because all data members in interfaces are public static final by default, they are constants (assign the values at the time of declaration).

Can constructor be pure virtual?

Constructors cannot be virtual. You could go for two stage construction and provide a pure virtual Initialise() method that is called after the constructor.

Why can’t we have virtual constructor?

Constructor can not be virtual, because when constructor of a class is executed there is no vtable in the memory, means no virtual pointer defined yet. Hence the constructor should always be non-virtual. Static functions are associated with the CLASS, not the objects (instances), so they don’t see a “this” pointer.

What happens if destructor is not virtual?

Deleting a derived class object using a pointer of base class type that has a non-virtual destructor results in undefined behavior. To correct this situation, the base class should be defined with a virtual destructor. For example, following program results in undefined behavior.

Can we inherit static method in Java?

Static methods in Java are inherited, but can not be overridden. If you declare the same method in a subclass, you hide the superclass method instead of overriding it. Static methods are not polymorphic. At the compile time, the static method will be statically linked.

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