第一步：編寫Java端代碼

定義一個Java類

public class TestNativeDemo {
 
    // 聲明本地方法
    public native String testJni(String arg);
 
    static {
        // 加載DLL文件
        System.loadLibrary("TestNativeDemoCPP");
    }
 
    public static void main(String args[]) {
        TestNativeDemo ob = new TestNativeDemo();
        // 調用本地方法
        String result = ob.testJni("Hello,Jni"); // call a native method
        System.out.println("TestNativeDemo.testJni=" + result);
    }
}

編譯之后在生成TestNativeDemo.class的bin目錄下執行javah TestNativeDemo命令生成頭文件TestNativeDemo.h

----------------------------------------------

/* DO NOT EDIT THIS FILE - it is machine generated */sky7034
#include <jni.h>
/* Header for class TestNativeDemo */
 
 
#ifndef _Included_TestNativeDemo //避免重復包含頭文件  
#define _Included_TestNativeDemo
#ifdef __cplusplus //c++編譯環境中才會定義__cplusplus  
extern "C" { //告訴編譯器下面的函數是c語言函數（因為c++和c語言對函數的編譯轉換不一樣，主要是c++中存在重載）   
 
#endif
/*
 * Class:     TestNativeDemo
 * Method:    testJni
 * Signature: (Ljava/lang/String;)Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_TestNativeDemo_testJni
  (JNIEnv *, jobject, jstring);
 
#ifdef __cplusplus
}
#endif
#endif