Standard constructor

When we create an object of a class that does not contain any constructor definition (such as the first version of the Person class), the so-called standard constructor is called.

• The standard constructor is a constructor without arguments generated automatically by the compiler for all those classes that do not contain any constructor definition.
• It leaves the instance variables initialized to their default value, which is the value assigned automatically by the run-time support when the memory location associated to the variable is being reserved.
• The standard constructor is automatically inhibited by the compiler when the definition of any constructor (with or without arguments) is explicitly present in the class. In particular, the programmer can also explicitly define a constructor without arguments that replaces the standard constructor.

For example, for the class Person, we could define the following constructor without arguments:

public Person() { // constructor without arguments
  name = "John Smith";
  residence = null;
}

Note: It does not always make sense to define for a class a constructor without arguments. For example, the definition of a constructor without arguments for the class Person can certainly be questioned.