help (JNI)!! can't retrieve StringBuffer::append(String)'s method ID!!

Posted on 2001-09-03
Last Modified: 2013-12-29
I'm trying to call the method StringBuffer append(String) in the JNI native method, but I couldn't retrieve the append(String)'s method, what's wrong with my code below :

mID= pEnv->GetMethodID(sbcls,"append","(Ljava/lang/String;)Ljava/lang/StringBuffer");

(sbcls is the StringBuffer's class id)
I could use the above pEnv,sbcls to retrieve the void setLength(int)'s methods ID, but it just don't work on StringBuffer append(String), why ? help please!!

Question by:eugeneng
  • 2

Expert Comment

ID: 6452246
Hi eugeneng,

jclass  sbcls =     pEnv->FindClass("class name");

if(sbcls == NULL)
     printf("FindClass fail");
jstring jmsgIn = pEnv->NewStringUTF("abc");

pEnv->GetMethodID(sbcls, "append", "(Ljava/lang/String;)V"),


make sure append method is'nt static method.

best regard!



Author Comment

ID: 6455116
this doesn't work, because "append(String)" return StringBuffer, you won't be able to retrieve method ID of "void append(String)" because this function doesn't exist, to prove that, I tried your code, it failed.

Accepted Solution

muhotrepius earned 50 total points
ID: 6456406
Dude you missed one ; at the end of the return type.
It should be "Ljava/land/StringBuffer;"
This works on my NT :

   jclass strbuf;
   strbuf = (*env)->FindClass(env, "java/lang/StringBuffer");
   if(NULL == strbuf)
      MessageBox(NULL, "Cannot find class", "Error", MB_OK);
   else {
      jmethodID append = (*env)->GetMethodID(env, strbuf, "append", "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
      if(NULL == strbuf)
         MessageBox(NULL, "Cannot find method", "Error", MB_OK);
         MessageBox(NULL, "OK", "Ok", MB_OK);

Author Comment

ID: 6456492
u r right muhotrepius, thanx

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