Shulou(Shulou.com)06/02 Report--

This article introduces the knowledge about "what are the language characteristics of DEFAULT mechanism in ABAP and Java". In the operation process of actual cases, many people will encounter such difficulties. Next, let Xiaobian lead you to learn how to deal with these situations! I hope you can read carefully and learn something!

New syntax for ABAP 740:

The code above is equivalent to:

DATA: ls_data LIKE LINE OF it_data.READ TABLE it_data INTO ls_data WITH KEY object_ext = cl_crm_prodil_bo_names=>gc_prod_root.CALL METHOD add_data EXPORTING ir_child_object = ir_root_object is_data = ls_data.

This shows that the new syntax is simpler and can write 3 lines less code. However, there is a flaw in this way. Under the new syntax, if there is no record with cl_crm_prodil_bo_names=>gc_prod_root in the object_ext table in it_data, the program execution will be terminated and the exception CX_SY_ITAB_LINE_NOT_FOUND will be thrown.

ABAP also has a solution for this situation.

Line 17 of the following figure throws an exception, while line 19 does not. It is easy to understand semantically: if there is no record named Spring2 in the inner table lt_data, a structure specified by the developer using the DEFAULT keyword is returned as the default value.

Java 8 has a similar mechanism. To avoid the infamous NullPointerException, Java developers need to check that an object instance is not null before using an object instance method:

if( xx != null ){ xx.doSomething();}

In Java 8, a new utility class Optional is provided in the package java.util, see how it works.

The filter method on line 11 should semantically return null because the string constant I initialized on line 10 is obviously longer than 6. But the object calling the filter method is an Optional object, so the filter method ends up returning an Optional object wrapped around a null. As shown in the debugger below:

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