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Can a class not have a default constructor?
If constructors are explicitly defined for a class, but they are all non-default, the compiler will not implicitly define a default constructor, leading to a situation where the class does not have a default constructor. This is the reason for a typical error, demonstrated by the following example.
How can we use constructor in abstract class?
Abstract classes require constructors to enforce a design contract using which objects can be initialized. Constructor can be used to setting up an attribute of the base class. This attribute will be available in subclass by inheritance. Before using this attribute, using the constructor it can be initialized.
Can abstract class have multiple constructor?
Yes, an abstract class can have a constructor in Java. The compiler automatically adds the default constructor in every class either it is an abstract class or concrete class. You can also provide a constructor to abstract class explicitly.
Is default constructor always called?
A class does so by defining a special constructor, known as the default constructor. This constructor is called the default constructor because it is run “by default;” if there is no initializer, then this constructor is used. The default constructor is used regardless of where a variable is defined.
What happens if an abstract method is not defined?
A method which does not have body is known as abstract method. To use an abstract method, you need to inherit it by extending its class and provide implementation to it. A class which contains 0 or more abstract methods is known as abstract class.
Is there a constructor for an abstract class?
Yes, an Abstract class always has a constructor. If you do not define your own constructor, compiler will give a default constructor to the Abstract class. Above holds true for all classes – nested, abstract, anonymous, etc.
Can a concrete class have a constructor in Java?
The concrete class TimesWhat has a constructor that allows the caller to specify the value. Abstract constructors will frequently be used to enforce class constraints or invariants such as the minimum fields required to setup the class.
What are the properties of an abstract class?
Properties of an abstract class: An abstract can have an abstract and non-abstract method. It must be declared with an abstract keyword. It can have a constructor, static methods.
Is the object of an abstract class instantiated?
The object of the abstract class can’t be instantiated it means you can’t create an abstract class object directly but you can create its object by reference to its child class. Constructor: Constructor is always called by its class name in a class itself.