The Java Native Interface (JNI) - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 592

This command produces a file named javatech - jni22 - JNIHelloWorld.h
in the build/headers directory. Notice the naming scheme in which the pack-
age name ( javatech.jni22 ) and class name ( JNIHelloWorld ) are used
with underscore characters replacing the dots.
Let's examine the generated header file (the formatting has been modified
slightly from the actual generated source to better fit the page):
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class javatech - jni22 - JNIHelloWorld */
#ifndef - Included - javatech - jni22 - JNIHelloWorld
#define - Included - javatech - jni22 - JNIHelloWorld
#ifdef - cplusplus
extern "C"{
#endif
/*
* Class: javatech - jni22 - JNIHelloWorld
* Method: nativeHelloWorld
* Signature: ()V
*/
JNIEXPORT void JNICALL
Java - javatech - jni22 - JNIHelloWorld - nativeHelloWorld (
JNIEnv *, jobject);
/*
* Class: javatech - jni22 - JNIHelloWorld
* Method: nativeHelloWorldStatic
* Signature: ()V
*/
JNIEXPORT void JNICALL
Java - javatech - jni22 - JNIHelloWorld - nativeHelloWorldStatic (
JNIEnv *, jclass);
#ifdef - cplusplus
}
#endif
#endif
This may look unwieldy at first (like we said, JNI code is “ugly”), but there are two
important lines here - the two that begin with JNIEXPORT void JNICALL .
These give the signatures of the two native C functions that must be used in
the implementation source. We see that each method name declared in the Java
source code ( nativeHelloWorld and nativeHelloWorldStatic ) gets
converted into a long function name beginning with Java - followed by the fully-
qualified method name, again with dots replaced by underscores. This lengthy