REPORT demo_list_hide NO STANDARD PAGE HEADING.*-----------------------------class superclass definition. 定义基类 public section. data para(30) type c value 'this is super method!'. methods write_first. methods write.endclass.
class subclass definition inheriting from superclass. 定义派生类 public section. methods write_first redefinition. 定义重载方法 methods write_second.endclass.
class superclass implementation. method write_first. write:/ para. skip. endmethod. method write. write:/ 'super method not inheriting!'. endmethod.endclass.
class subclass implementation. method write_first. call method super->write_first. 通过super调用基类的方法，反之me endmethod. method write_second. para = 'the redifinition method!'. call method me->write_first. 通过me调用自身的方法 endmethod.endclass.
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*-基类有多个派生类的时候，所有操作都在派生类中实现，并不需要通过基类定义对象实例，可以将基类定义为一个模板，声明为抽象类。
*-抽象类包含至少一个抽象方法，不能通过create object声明对象实例。抽象方法只包含方法的定义，不包含具体的实现，实现在子类中。
class superclass2 definition abstract. 定义一个抽象类 public section. data abs(40) value 'this is a super abstract!'. methods write_first abstract.定义抽象方法endclass.class subclass2 definition inheriting from superclass2. public section. methods write_first redefinition. methods write_second.endclass.class subclass2 implementation. method write_first. write:/ 'abstract:'. write:/ abs. skip. endmethod. method write_second. write:/ 'this is the second method.'. endmethod.endclass.data new2 type ref to subclass2.
data new type ref to subclass.
start-of-selection. create object new. call method: new->write_first, new->write_second, new->write.派生类的实例化对象可以调用自身的所有方法，而且可以调用基类的方法，但是方法重载之后，不能通过实例化对象直接调用该方法，需用supper来实现。
create object new2.
call method: new2->write_first, new2->write_second.
最终类与最终方法：
最终类和最终方法都是不可以继承的，为了防止多级别的派生导致的语义语法冲突。
class finalclass definition final.
…………
methods final_write final.
endclass.
