Fujitsu has provided a jni testcase for java 1.2 which doesn't show Japanese SJIS codes
3rd. argument of icv.convertExtended() in convertEx.java is sjis.

I can find in 4642283 Suggested Fix
+ classname = (char *)(*env)->GetStringUTFChars(env, mainClassName, 0);

This is the use of the function in convertEx.c from the testcase provided by Fujitsu
 srcString = (char *)((*env)->GetStringUTFChars(env, strSrc, NULL));
 fromCode = (char *)((*env)->GetStringUTFChars(env, strFrom, NULL));
 toCode = (char *)((*env)->GetStringUTFChars(env, strTo, NULL));
 printf("TEST convertExtended fromCode[%s] toCode[%s]\n",fromCode,toCode);

Testcase has been checked in Sun with Sol8/9 and java 1.2.2_10 and 1.4.1_02
We can see japanese characters in convertEx.java in the call to the jni function icv.convertExtended (using dtpad and gedit)

% java -version
java version "1.2.2"
Solaris VM (build Solaris_JDK_1.2.2_10, native threads, sunwjit)
% javac convertEx.java
% javah -jni convertEx
% cc -V
cc: Forte Developer 7 C 5.4 2002/03/09
% cc -G -I.
-I/usr/java1.2/include -I/usr/java1.2/include/solaris convertEx.c -o libconvertEx.so
"convertEx.c", line 78: warning: argument #2 is incompatible with
prototype:
        prototype: pointer to pointer to const char : "/usr/include/iconv.h", line 20
        argument : pointer to pointer to char
% java -Djava.library.path=. convertEx UTF-8 PCK
***** start
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [abcdefg]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [????A~^(o)U?N??]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?????????}]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING
[?@?A?B?C?D?E?F?G?H?I?_?`?a?b?c?d?e?f?g?h?i?j?k?l?m?n]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [???????????????????]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?o?p?q?r]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING
[??????}?????L???A~????????????????@?A?B?C?D?E?F?G?H?I?J?K?L?M?N]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?@?A?B?C?D?E?F?G?H?I?J?K?L?M?N]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?????????????A~^(o)U]
***** end [?????????????U]

% /usr/j2se/bin/java -version
java version "1.4.1_02"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1_02-b06)
Java HotSpot(TM) Client VM (build 1.4.1_02-b06, mixed mode)
% /usr/j2se/bin/java -Djava.library.path=. convertEx UTF-8 PCK
***** start
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [abcdefg]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [????A~^(o)U?N??]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?????????}]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING
[?@?A?B?C?D?E?F?G?H?I?_?`?a?b?c?d?e?f?g?h?i?j?k?l?m?n]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [???????????????????]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?o?p?q?r]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING
[??????}?????L???A~????????????????@?A?B?C?D?E?F?G?H?I?J?K?L?M?N]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?@?A?B?C?D?E?F?G?H?I?J?K?L?M?N]
TEST convertExtended fromCode[UTF-8] toCode[PCK]
TEST convertExtended CALLING [?????????????A~^(o)U]
***** end [??????????????????U]

###@###.### 2003-06-25
see also original sjis code in attachment (kanji.gif)