In JNI how to call Java methods from native language methods

Question

I just build the example of java tutorial on
http://java.sun.com/docs/books/tutorial/native1.1/implementing/method.html
but when I excute, it says:
Callbacks.c:1:syntax error before 'void'
Callbacks.c:2:parse error before '*'
Callbacks.c:In function 'Java_Callbacks_nativeMethod':
attached:
Callbacks.c
JNIEXPORT void JNICALL
Java_Callbacks_nativeMethod(JNIEnv *env, jobject obj, jint depth)
jclass cls = (*env)->GetObjectClass(env, obj);
jmethodID mid = (*env)->GetMethodID(env, cls, "callback", "(I)V");
if (mid == 0) {
return;
printf("In C, depth = %d, about to enter Java\n", depth);
(*env)->CallVoidMethod(env, obj, mid, depth);
printf("In C, depth = %d, back from Java\n", depth);
Callbacks.java
class Callbacks {
private native void nativeMethod(int depth);
private void callback(int depth) {
if (depth < 5) {
System.out.println("In Java, depth = " + depth + ", about to enter C");
nativeMethod(depth + 1);
System.out.println("In Java, depth = " + depth + ", back from C");
} else
System.out.println("In Java, depth = " + depth + ", limit exceeded");
public static void main(String args[]) {
Callbacks c = new Callbacks();
c.nativeMethod(0);
static {
System.loadLibrary("MyImpOfCallbacks");

Answer 1

Looks like you havn't included the jni header file. Add this to the top of the .c file:
#include "jni.h"