Convert ABAP to Java

Question

Hello everyone,
right now i have an ABAP-function-module which i have to convert into Java-Code.
My problem is: i don't really understand ABAP so i have some questions.
The part which i don't understand is this:
READ TABLE t_ctab INDEX f_char.
    IF sy-subrc EQ 0.
    CONCATENATE f_werks t_ctab-char1 INTO f_werks.
   ENDIF.
What happens here?
Thanks in advance.

Answer 1

Ok, thank you.
Hopefully the last question:
The next ABAP-Code snippet contains the main part which i have to translate.
It converts decimals into a char-sequence with a length of 4.
Example: 0010000 -> $),D
FORM umrechnung_dezimal_to_basis
                    TABLES   t_ctab STRUCTURE t_ctab
                     USING   i_werks
                    CHANGING o_werks.
*Read length of decimal
  DATA:
  f_stel TYPE i,     
  f_lines TYPE i.
  DATA:
  f_potenz TYPE i,
  f_rest TYPE i.
  DATA:
  f_char TYPE i. "position of char
  DATA:
  f_werks TYPE ty_out-werks_i.
*determine base
  DESCRIBE TABLE t_ctab LINES f_lines.
*delete leading zeros
  WRITE i_werks TO f_werks NO-ZERO.
*delete leading whitespaces
  CONDENSE f_werks.
*length of decimal
  f_stel = strlen( f_werks ).
decimal to convert
  f_rest = f_werks.
biggest potency
  f_potenz = f_stel - 1.
  CLEAR: f_werks.
conversion
  DO f_stel TIMES.
    f_char = trunc( f_rest / f_lines ** f_potenz ) + 1.
    READ TABLE t_ctab INDEX f_char.
    IF sy-subrc EQ 0.
      CONCATENATE f_werks t_ctab-char1 INTO f_werks.
    ENDIF.
    f_rest   = f_rest MOD ( f_lines ** f_potenz ).
    f_potenz = f_potenz - 1.
  ENDDO.
  PERFORM format_i TABLES t_ctab
                 CHANGING f_werks
                          o_werks.
ENDFORM.                    " conversion