In JNI, how do I cache the class, methodID, and fieldIDs per IBM's performance recommendations?

Question

I read on on IBM that

To access Java objects\' fields and invoke their methods, native code must make calls to FindClass(), GetFieldID(), GetMethod

Answer 1

For simple case, I use static fields in the C code, initialized with an initId method called from my java classes :

package demo;
public class WithNatives {

 static {
   initIDs();
 }

 private static native void initIDs();

}

And in C :

static jmethodID methodId;

void JNICALL Java_demo_WithNatives_initIDs(JNIEnv *env, jclass clazz)
{
   // initialize methodId
}