First JNI

http://hi.baidu.com/fwmf/blog/item/849c1cf7ece36c3a730eecee.html

ubuntu 11.04：
cd to a dir：
1,vim HelloWorld.java:

public class HelloWorld {

        private native void print();

        public static void main(String[] args) {
                new HelloWorld().print();
        }

        static {
                System.loadLibrary("HelloWorld");
        }
}

2,然后： javac HelloWorld.java
(make sure CLASSPATH包含.)

3,javah -jni HelloWorld
to gen a HelloWorld.h file
4,vim HelloWorld.c :

#include <jni.h>
#include <stdio.h>
#include "HelloWorld.h"

JNIEXPORT void JNICALL Java_HelloWorld_print(JNIEnv *env,jobject obj){
        printf("Hello World!\n");
        return ;
}

5 cp $JAVA_HOME/include/*.h & include/linux/*.h to /usr/include/
then do:
gcc -fPIC -shared -o libHelloWorld.so HelloWorld.c
or just use :
gcc -I $JAVA_HOME/include -I $JAVA_HOME/include/linux  -fPIC -shared -o libHelloWorld.so HelloWorld.c

note don't use -c for HelloWorld.c

6 java -Djava.library.path=. HelloWorld
OK