类定义
ABAP 类可以全局或局部声明。全局类可以被 ABAP 存储库中的任何对象使用。相比之下，局部类只能在其声明的范围内使用。例子如下：
CLASS lcl_abap_class DEFINITION.
PUBLIC SECTION.
PROTECTED SECTION.
PRIVATE SECTION.
ENDCLASS.
CLASS lcl_abap_class IMPLEMENTATION.
ENDCLASS.
局部类的构造函数、方法定义与实现：
CLASS lcl_abap_class DEFINITION.
PUBLIC SECTION.
METHODS: constructor,
method1.
PROTECTED SECTION.
PRIVATE SECTION.
METHODS: method2,
method3.
ENDCLASS.
CLASS lcl_abap_class IMPLEMENTATION.
METHOD constructor.
"Logic
ENDMETHOD.
METHOD method1.
"Logic
ENDMETHOD.
METHOD method2.
"Logic
method3( ).
ENDMETHOD.
METHOD method3.
"Logic
ENDMETHOD.
ENDCLASS.
旧的方法调用：
DATA lo_abap_class TYPE REF TO lcl_abap_class.
CREATE OBJECT lo_abap_class. "Constructor call
lo_abap_class->method1( ).
推荐使用新的方法调用：
DATA(lo_abap_class) = NEW lcl_abap_class( ).
lo_abap_class->method1( ).
或者：
DATA lo_abap_class TYPE REF TO lcl_abap_class.
lo_abap_class = NEW #( ).
lo_abap_class->method1( ).
继承 - 抽象和 Final 方法和类
METHODS 和 CLASS 语句中的 ABSTRACT 和 FINAL 添加允许您定义抽象和 Final 方法或类。
抽象方法是在抽象类中定义的，并且不能在该类中实现。相反，它是在该类的子类中实现的。抽象类不能被实例化。
Final 方法不能在子类中重新定义。Final 类不能有子类。
类实现：
CLASS lcl_abstract DEFINITION ABSTRACT.
PUBLIC SECTION.
METHODS: abstract_method ABSTRACT,
final_method FINAL
normal_method.
ENDCLASS.
CLASS lcl_abstract IMPLEMENTATION.
METHOD final_method.
"This method can't be redefined in child class!
ENDMETHOD.
METHOD normal_method.
"Some logic
ENDMETHOD.
"We can't implement abstract_method here!
ENDCLASS.
CLASS lcl_abap_class DEFINITION INHERITING FROM lcl_abstract.
PUBLIC SECTION.
METHODS: abstract_method REDEFINITION,
abap_class_method.
ENDCLASS.
CLASS lcl_abap_class IMPLEMENTATION.
METHOD abstract_method.
"Abstract method implementation
ENDMETHOD.
METHOD abap_class_method.
"Logic
ENDMETHOD.
ENDCLASS.
方法调用：
DATA(lo_class) = NEW lcl_abap_class( ).
lo_class->abstract_method( ).
lo_class->normal_method( ).
lo_class->abap_class_method( ).
lo_class->final_method( ).
继承定义
继承允许你从现有的类派生出一个新类。要做到这一点，需要使用 CLASS subclass DEFINITION INHERITING FROM superclass. 语句。新类子类继承现有类超类的所有组件。新类称为派生类的子类。原来的类称为新类的超类。一个类可以有多个直接子类，但只能有一个直接超类。
类继承
CLASS lcl_vehicle DEFINITION.
ENDCLASS.
CLASS lcl_vehicle IMPLEMENTATION.
ENDCLASS.
CLASS lcl_car DEFINITION INHERITING FROM lcl_vehicle.
ENDCLASS.
CLASS lcl_car IMPLEMENTATION.
ENDCLASS.
带参数的方法（Importing, Changing, Exporting）
带参数的类定义与类实现：
CLASS lcl_abap_class DEFINITION.
PRIVATE SECTION.
METHODS method1 IMPORTING iv_string TYPE string
CHANGING cv_string TYPE string
EXPORTING ev_string TYPE string.
ENDCLASS.
CLASS lcl_abap_class IMPLEMENTATION.
METHOD method1.
cv_string = iv_string.
ev_string = 'example'.
ENDMETHOD.
ENDCLASS.
方法调用：
method1 (
EXPORTING iv_string = lv_string
IMPORTING ev_string = lv_string2
CHANGING cv_string = lv_string3
).
带返回参数的方法
类实现：
CLASS lcl_abap_class DEFINITION.
PRIVATE SECTION.
METHODS method1 RETURNING VALUE(rv_string) TYPE string.
ENDCLASS.
CLASS lcl_abap_class IMPLEMENTATION.
METHOD method1.
rv_string = 'returned value'.
ENDMETHOD.
ENDCLASS.
方法调用：
lv_string = method1( ).
请注意，使用 RETURNING 声明的参数仅支持按值传递。
