Get Started with ABAP Programming on SAP BTP

Using Control Structures in ABAP

Objectives
After completing this lesson, you will be able to:

After completing this lesson, you will be able to:

  • Implement conditional branching
  • Implement Iterations
  • Handle Exceptions

Implementing Conditional Branching

A conditional branching is a control structure that allows you to make the execution of code dependent on logical conditions.

Let's look at the different techniques of conditional branching.

Try It Out: Conditional Branching

  1. Like in the first exercise of this course, create a new global class that implements interface IF_OO_ADT_CLASSRUN.
  2. Copy the following code snippet to the implementation part of method if_oo_adt_classrun~main( ):
    Code snippet
    
* Declarations
**********************************************************************

    CONSTANTS c_number TYPE i VALUE 0.
*    CONSTANTS c_number TYPE i VALUE 1.
*    CONSTANTS c_number TYPE i VALUE 2.
*    CONSTANTS c_number TYPE i VALUE -1.
*    CONSTANTS c_number TYPE i VALUE -2.

* Example 1: Simple IF ... ENDIF.
**********************************************************************

    out->write(  `--------------------------------` ).
    out->write(  `Example 1: Simple IF ... ENDIF.` ).
    out->write(  `-------------------------------` ).

    IF c_number = 0.
      out->write( `The value of C_NUMBER equals zero`   ).
    ELSE.
      out->write( `The value of C_NUMBER is NOT zero`   ).
    ENDIF.

* Example 2: Optional Branches ELSEIF and ELSE
**********************************************************************

    out->write(  `--------------------------------------------` ).
    out->write(  `Example 2: Optional Branches ELSEIF and ELSE` ).
    out->write(  `--------------------------------------------` ).

    IF c_number = 0.
      out->write( `The value of C_NUMBER equals zero`            ).
    ELSEIF c_number > 0.
      out->write( `The value of C_NUMBER is greater than zero`   ).
    ELSE.
      out->write( `The value of C_NUMBER is less than zero`      ).
    ENDIF.

* Example 3: CASE ... ENDCASE
**********************************************************************

    out->write(  `---------------------------` ).
    out->write(  `Example 3: CASE ... ENDCASE` ).
    out->write(  `---------------------------` ).

    CASE c_number.
      WHEN 0.
        out->write( `The value of C_NUMBER equals zero`             ).
      WHEN 1.
        out->write( `The value of C_NUMBER equals one`              ).
      WHEN 2.
        out->write( `The value of C_NUMBER equals two`              ).
      WHEN OTHERS.
        out->write( `The value of C_NUMBER equals non of the above` ).
    ENDCASE.
    Copy code
  3. Press CTRL + F3 to activate the class and F9 to execute it as a console app.
  4. Analyze the console output. Play around with the source code to get familiar with the concepts; Uncomment different declarations of constant c_number with different values to see, which branches of the code get executed.

Implementing Iterations

Iterations are control structures that define a block of code which is executed several times.

Watch this video to learn how.

Try It Out: Iterations

  1. Like in the first exercise of this course, create a new global class that implements interface IF_OO_ADT_CLASSRUN.
  2. Copy the following code snippet to the implementation part of method if_oo_adt_classrun~main( ):
    Code snippet
    
* Declarations
**********************************************************************

    CONSTANTS c_number TYPE i VALUE 3.
*    CONSTANTS c_number TYPE i VALUE 5.
*    CONSTANTS c_number TYPE i VALUE 10.

    DATA number TYPE i.

* Example 1: DO ... ENDDO with TIMES
**********************************************************************

    out->write(  `----------------------------------` ).
    out->write(  `Example 1: DO ... ENDDO with TIMES` ).
    out->write(  `----------------------------------` ).

    DO c_number TIMES.
      out->write(  `Hello World` ).
    ENDDO.

* Example 2: DO ... ENDDO with Abort Condition
**********************************************************************

    out->write(  `-------------------------------` ).
    out->write(  `Example 2: With Abort Condition` ).
    out->write(  `-------------------------------` ).

    number = c_number * c_number.

    " count backwards from number to c_number.
    DO.

      out->write( |{ sy-index }: Value of number: {  number }| ).
      number = number - 1.

      "abort condition
      IF number <= c_number.
        EXIT.
      ENDIF.

    ENDDO.
    Copy code
  3. Press CTRL + F3 to activate the class and F9 to execute it as a console app.
  4. Analyze the console output. Play around with the source code to get familiar with the concepts; Uncomment different declarations of constant c_number to see how the different values affect the result.

Handling Exceptions

Exceptions

What are exceptions? Let's take a look.

Exception Handling

Now that you have learned about exceptions, let's see how you can handle them.

Try It Out: Exception Handling

  1. Like in the first exercise of this course, create a new global class that implements interface IF_OO_ADT_CLASSRUN.
  2. Copy the following code snippet to the implementation part of method if_oo_adt_classrun~main( ):
    Code snippet
    
* Declarations
**********************************************************************
    DATA result TYPE i.

    DATA numbers TYPE TABLE OF i.

* Preparation
**********************************************************************

    APPEND 123 TO numbers.

* Example 1: Conversion Error (no Number)
**********************************************************************

    CONSTANTS c_text TYPE string VALUE 'ABC'.
*    CONSTANTS c_text TYPE string VALUE '123'.

    out->write(  `---------------------------` ).
    out->write(  `Example 1: Conversion Error` ).
    out->write(  `---------------------------` ).

    TRY.
        result = c_text.
        out->write( |Converted content is { result }|  ).
      CATCH cx_sy_conversion_no_number.
        out->write( |Error: { c_text } is not a number!| ).
    ENDTRY.

* Example 2: Division by Zero
**********************************************************************

    CONSTANTS c_number TYPE i VALUE 0.
*    CONSTANTS c_number TYPE i VALUE 7.

    out->write(  `---------------------------` ).
    out->write(  `Example 2: Division by Zero` ).
    out->write(  `---------------------------` ).

    TRY.
        result = 100 / c_number.
        out->write( |100 divided by { c_number } equals { result }| ).
      CATCH cx_sy_zerodivide.
        out->write(  `Error: Division by zero is not defined!` ).
    ENDTRY.

* Example 3: Itab Error (Line Not Found)
**********************************************************************

    CONSTANTS c_index TYPE i VALUE 2.
*    CONSTANTS c_index TYPE i VALUE 1.

    out->write(  `-------------------------` ).
    out->write(  `Example 3: Line Not Found` ).
    out->write(  `-------------------------` ).

    TRY.
        result = numbers[ c_index ].
        out->write( |Content of row { c_index } equals { result }| ).
      CATCH cx_sy_itab_line_not_found.
        out->write(  `Error: Itab has less than { c_index } rows!` ).
    ENDTRY.


* Example 4: Combination of Different Exceptions
**********************************************************************
*    CONSTANTS c_char TYPE c LENGTH 1 VALUE 'X'.
*    CONSTANTS c_char TYPE c length 1 value '0'.
    CONSTANTS c_char TYPE c LENGTH 1 VALUE '1'.
*    CONSTANTS c_char TYPE c length 1 value '2'.

    out->write(  `----------------------` ).
    out->write(  `Example 4: Combination` ).
    out->write(  `----------------------` ).

    TRY.
        result = numbers[ 2 / c_char ].
        out->write( |Result: { result } | ).
      CATCH cx_sy_zerodivide.
        out->write( `Error: Division by zero is not defined`  ).
      CATCH cx_sy_conversion_no_number.
        out->write( |Error: { c_char } is not a number! | ).
      CATCH cx_sy_itab_line_not_found.
        out->write( |Error: Itab contains less than { 2 / c_char } rows| ).
    ENDTRY.
    Copy code
  3. Press CTRL + F3 to activate the class and F9 to execute it as a console app.
  4. Analyze the console output. Play around with the source code to get familiar with the concept:
    • Comment the exception handling to make the system raise a runtime error.
    • Change the values of constants c_number, c_text, c_index, and c_charin a way that no exceptions are raised.

Save progress to your learning plan by logging in or creating an account

login / register
Continue to next lesson