Interfaces concept ...Urgent?

Question

Hi all,
As we all know multiple inheritance cannot be achieved in ABAP classes, so we need to take INTERFACES approach, I am trying to do from the below mentioned code.
*&            INTERFACE Stu_course
INTERFACE stu_course.
  DATA : course_id.
  METHODS: max_student,
           add_student,
           drop_student.
ENDINTERFACE.
*&          Class cl_course
CLASS cl_course DEFINITION ABSTRACT.
  PUBLIC SECTION.
  INTERFACES stu_course.
  PRIVATE SECTION.
  DATA : count TYPE i.
ENDCLASS.
CLASS cl_course IMPLEMENTATION.
  METHOD stu_course~add_student.
    WRITE: / 'Student added'.
  ENDMETHOD.
  METHOD stu_course~drop_student.
    WRITE: / 'Student Dropped'.
  ENDMETHOD.
  METHOD stu_course~max_student.
    count = count + 1.
    IF count GT 10.
    write: / 'maximum number of student reached'.
    ENDIF.
  ENDMETHOD.
ENDCLASS.
*&            Class cl_student
CLASS cl_student DEFINITION. "INHERITING FROM cl_university_member.(currently not mentioned)
   PUBLIC SECTION.
   DATA : student_id type i.
   INTERFACES stu_course.
     METHODS:register_course
              IMPORTING course TYPE REF TO cl_course,
            withdraw_course
              IMPORTING course TYPE REF TO cl_course.
ENDCLASS.
CLASS cl_student IMPLEMENTATION.
METHOD register_course.
"Here i want to call the definition of method "add_student" of class cl_course without inheritance, so that i can achieve multiple inheritance."
ENDMETHOD.
ENDCLASS.
Class cl_student wants to inherit the definition of methods like             add_student,drop_student from class cl_course.Is this posible n how?
Thanks n Regards
Rohit

Answer 1

hi rohit,
  see below details regarding Intefaces,
     Interface
     Simple use of an interface
Theme     This program will show simple use of an interface with its own data and methods and how it is implemented in a class. It will also show that there can be methods of same name for an interface and the class implementing the interface.
Program Desc     This program contains an interface I1 with attribute : NUM an method : METH1.
This interface is implemented in a class : C1 which also has its own method METH1.
An object OREF is created from class C1 and both the methods METH1 , one for class and another for interface is called using the object.
Dump     
report ysubdel .
interface i1.
data    : num type i .
methods : meth1.
endinterface.
class c1 definition.
  public section.
   methods : meth1.       “ class C1’s own method
   interfaces : i1.
endclass.
class c1 implementation.
  method : meth1.
   write:/5 'I am meth1 in c1'.
  endmethod.
  method i1~meth1.
   write:/5 'I am meth1 from i1'.
  endmethod.
endclass.
start-of-selection.
  data : oref type ref to c1.
  create object oref.
  write:/5 oref->i1~num.
  call method oref->meth1.
  call method oref->i1~meth1.
Output               0         
I am meth1 in c1   
I am meth1 from i1 
     Interfaces can only be implemented in the public section of a class
Theme     This program will show you that classes implementing an interface can only contain the features of the interface in its public section.
Program Description     In this program, class C1 is trying to accommodate interface I1 in its PRIVATE SECTION.
This creates a compilation error, establishing the theme.
Dump     report ysubdel .
interface i1.
methods : meth1.
endinterface.
class c1 definition.
  protected section.
   interfaces : i1.
endclass.
Output     Compilation error with error message :-
INTERFACES may only be implemented in the public section.
     A class with an interface should implement all the methods of that interface
Theme     This program will show that a class containing an interface should implement all the methods of the interface in its implementation section.
Program Descrip     Class C1 implements interface I1, which has got two methods , METH1 and METH2. But, in the IMPLEMENTATION section of class C1, only METH1 is implemented.
This program will create a compilation error, establishing the theme.
Dump     
report ysubdel .
interface i1.
methods : meth1 ,
           meth2 .
endinterface.
class c1 definition.
  public section.
   interfaces : i1.
endclass.
class c1 implementation.
  method i1~meth1.
   write:/5 'I am meth1 from i1'.
  endmethod.
endclass.
start-of-selection.
  data : oref type ref to c1.
   create object oref.
   call method oref->i1~meth1.
Output     Compilation error with error message :-
Implementation missing for method “I1~METH2”
if helpful please reward the points,
Aruna