/*filename native.ccommod: gcc -shared -o libnative.so native.c -I/usr/lib/jvm/java-1.7.0-openjdk-amd64/include -fPIC
*/
#include <stdio.h>
#include <jni.h>  /* /usr/lib/jvm/java-1.7.0-openjdk-amd64/include */int  c_hello( JNIEnv *env, jobject cls, jint num )
{printf("hello  c/c++ num=%d\r\n",num);return num*2;
}/* 2. java <--> C */static const JNINativeMethod methods[] = {{"hello","(I)I",(void *)c_hello},            /* java function  参数  c function*/
};JNIEXPORT jint JNICALLJNI_OnLoad( JavaVM *jvm, void *reserved )
{JNIEnv *env;jclass cls;/* 获取运行环境 */if((*jvm)->GetEnv(jvm,(void **)&env,JNI_VERSION_1_4))return JNI_ERR;/* 获取java中的类 */cls = (*env)->FindClass(env,"JNIDemo");if(cls==NULL)return JNI_ERR;/* 函数映射 */if((*env)->RegisterNatives(env, cls, methods,1)<0)return JNI_ERR;return JNI_VERSION_1_4;
}

/*
*   filename JNIDemo.java
*   commod: javac JNIDemo.java
* */
public class JNIDemo {static {/* 1. load */System.loadLibrary("native"); /*libnative.so*/}public native static  int hello( int num );public static  void main( String args[] ){/* 2. java <--> C *//* 3. call */System.out.println( hello(123) );}
}

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class JNIDemo */#ifndef _Included_JNIDemo
#define _Included_JNIDemo
#ifdef __cplusplus
extern "C" {
#endif
/** Class:     JNIDemo* Method:    hello* Signature: (I)I*/
JNIEXPORT void JNICALL Java_JNIDemo_hello(JNIEnv *, jclass);#ifdef __cplusplus
}
#endif
#endif