Concept of Constructor in ABAP OOPs

REPORT  zcl_oops_test.

*----------------------------------------------------------------------*
*       CLASS cl_constructor1 DEFINITION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS cl_constructor1 DEFINITION.
  PUBLIC SECTION.
    METHODS constructor IMPORTING num1 TYPE i.

ENDCLASS.                    "cl_constructor1 DEFINITION

*----------------------------------------------------------------------*
*       CLASS cl_constructor2 DEFINITION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS cl_constructor2 DEFINITION INHERITING FROM cl_constructor1.
  PUBLIC SECTION.
    METHODS constructor IMPORTING num2 TYPE i.

ENDCLASS.                    "cl_constructor2 DEFINITION

*----------------------------------------------------------------------*
*       CLASS cl_constructor1 IMPLEMENTATION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS cl_constructor1 IMPLEMENTATION.
  METHOD constructor.
    WRITE:/ 'Constructor Method'.
    WRITE:/ 'num1 = ' , num1.
*add 10 to p1.
  ENDMETHOD.                    "constructor
ENDCLASS.                    "cl_constructor1 IMPLEMENTATION

*----------------------------------------------------------------------*
*       CLASS cl_constructor2 IMPLEMENTATION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------

CLASS cl_constructor2 IMPLEMENTATION.

  METHOD constructor.
    super->constructor( num2 ).

  ENDMETHOD.                    "constructor
ENDCLASS.                    "cl_constructor2 IMPLEMENTATION

START-OF-SELECTION.

  DATA obj TYPE REF TO cl_constructor1.

  CREATE OBJECT obj
    EXPORTING
      num1 = 100.

Output