Before going through the differences between Abstract and Interface in Object Oriented ABAP please check below links to get understanding of Abstract and Interface concepts.
Difference between Abstract and Interface in OOPS ABAP
Simple Abstract class Example:
CLASS zcl_sample_code DEFINITION ABSTRACT. PUBLIC SECTION. METHODS: set_name ABSTRACT. METHODS: write_name. PRIVATE SECTION. DATA: my_name TYPE string. ENDCLASS. "zcl_sample_code DEFINITION CLASS zcl_sample_code IMPLEMENTATION. METHOD write_name. ENDMETHOD. "write_name ENDCLASS. "zcl_sample_code IMPLEMENTATION
Interface Example
INTERFACE zif_sales_order. methods: set_order_data IMPORTING iv_order_Data type string. methods: create_order. ENDINTERFACE. * class zcl_sales_order DEFINITION. PUBLIC SECTION. INTERFACEs: zif_order. ENDCLASS.
Differences between Abstract and Interface
| Abstract | Interface |
|---|---|
| It is a class which can't be instantiated. Can be instantiated only from subclass if subclass is not abstract | It is an entity which contains only declarations of methods and attributes |
| Multiple Inheritance is not supported. As OO ABAP supports only one super class we can have only one abstract class as super class. | Multiple Interfaces can be used in class definition and hence Multiple Inheritance is supported |
| It is not mandatory to redefine the non abstract method added in abstract class in all subclasses that inherits the abstract super class | Any new method included in interface must be implemented in all the classes which uses the interface otherwise runtime error will occur |
| Since abstract class can contain abstract and non abstract methods, we can include default logic in non abstract method of abstract super class. All subclasses will inherit this logic. | Since interface contains only empty method declarations we can't include a default logic in Interface |
| We can set the visibility of each component in Abstract class | All interface components are public by default |