[ABAP] ALV column header

DATA: o_salv TYPE REF TO cl_salv_table.

cl_salv_table=>factory( IMPORTING r_salv_table = o_salv
                        CHANGING  t_table      = l_lines ).

LOOP AT o_salv->get_columns( )->get( ) REFERENCE INTO DATA(l_column).
  DATA(lo_column) = CAST cl_salv_column( l_column->r_column ).
  lo_column->set_fixed_header_text( 'L' ).
ENDLOOP.

o_salv->get_columns( )->get_column( 'TEST1' )->set_long_text( 'Test1 Header' ).
o_salv->get_columns( )->get_column( 'TEST2' )->set_long_text( 'Test2 Header' ).

o_salv->get_columns( )->get_column( 'TEST1' )->set_output_length( 30 ). "to increase the column width

  TRY.
      cl_salv_table=>factory( IMPORTING r_salv_table = DATA(lo_alv)
                               CHANGING t_table      = ausgabe_tab ).

      lo_alv->get_columns( )->get_column( 'TEST1' )->set_long_text( 'Test1 Header' ).
      lo_alv->get_columns( )->set_optimize( abap_true ).

      lo_alv->display( ).
    CATCH cx_salv_msg.
  ENDTRY.