Parent and child constructor in Java

The compiler doesn’t ever enforce the existence of a default constructor. You can have any kind of constructor as you wish. For some libraries or frameworks it might be necessary for a class to have a default constructor, but that is not enforced by the compiler .

The arguments of a constructor can only be found by type, not by name, so there is no way for the framework to reliably match properties to constructor args. Therefore, they require a no-arg constructor to create the object, then can use the setter methods to initialise the data .

In both Java and C#, a “default constructor” refers to a nullary constructor that is automatically generated by the compiler if no constructors have been defined for the class . The default constructor implicitly calls the superclass’s nullary constructor, then executes an empty body.

If a class is not required to initialize its data member or does not contain data member, there is no need to write empty constructor explicitly . On class object creation, default constructor implicitly called will be enough. In below class, default constructor will be called on object creation of the class.