Java 在ABAP面向对象接口中的默认静态方法实现

不幸的是，这在ABAP中是不可能的.

接口contains only definitions和实际实现必须在实现该接口的类中提供.接口的所有方法都是抽象的(即，它们是完全定义的，包括它们的签名，但没有实现).

与类不同，它根本不是接口does not have an implementation section.默认情况下，所有组件都在公共部分，那里有no visibility sections个组件，界面的所有组件都是可见的.

接口可以包含以下组件:

• TYPES、DATA、CLASS-DATA、CONSTANTS:数据类型和数据对象
• METHODS, CLASS-METHODS, EVENTS, CLASS-EVENTS: methods and events
  interfaces provide fewer variants than classes for declarations of methods: no constructors, test methods, or AMDP function implementations are allowed
• INTERFACES: inclusion of component interfaces;
  ALIASES: alias names for components of interfaces

As we can see CLASS-METHODS indeed allows to define static method declarations, and the static methods are just NOT instance specific. It means that when a class implements such an interface, the methods defined as static do not require an instance to access / call them and they rather can be called on the class itself like class_name=>interface_name~static_method_name.
So actually the purpose of declaring a method as static in an interface definition is to create an agreement that a particular method will not depend on an instance to work.

然而，还有PUBLIC和DEFAULT个关键字可能会在接口定义中使用，这在一开始可能会导致混淆.

接口定义如下所示:

INTERFACE intf [PUBLIC].
    [components]
ENDINTERFACE.

加法PUBLIC使接口成为类库的全局接口，并且只能用于接口池的全局接口，并且在创建全局接口时由类构建器创建.

从Release 7.40, SP08开始提供关键字DEFAULT

METHODS meth [ABSTRACT|FINAL] | [DEFAULT IGNORE|FAIL] ...
CLASS-METHODS meth [DEFAULT IGNORE|FAIL] ...

语句METHODS和CLASS-METHODS的加法DEFAULT可用于使这些方法成为可选的.实现接口时在类中显式显示的可选接口方法does not need to be implemented.相反，在定义中为非实现方法的调用指定了默认行为:

• DEFAULT IGNORE-行为与使用空体实现时的行为相同
• DEFAULT FAIL - raise an exception of the class CX_SY_DYN_CALL_ILLEGAL_METHOD
  in case if not handled, the runtime error CALL_METHOD_NOT_IMPLEMENTED is raised

当然，您可以使用继承来实现基本方法，使用实现的方法创建(抽象)类，并在必要时在子类(关键字方法)中重新植入/覆盖它们.REDIFINITION).