main.h文件
#ifndef __MAIN_H__
#define __MAIN_H__

#include <windows.h>

/*  To use this exported function of dll, include this header
 *  in your project.
 */

#ifdef BUILD_DLL
    #define DLL_EXPORT __declspec(dllexport) __stdcall
#else
    #define DLL_EXPORT __declspec(dllimport) __stdcall
#endif

#ifdef __cplusplus
extern "C"
{
#endif

int DLL_EXPORT add(int a,int b);

#ifdef __cplusplus
}
#endif

#endif // __MAIN_H__

main.cpp

#include "main.h"

// a sample exported function
int DLL_EXPORT add(int a ,int b)
{
    return a+b;
}

extern "C" DLL_EXPORT BOOL APIENTRY DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
{
    switch (fdwReason)
    {
        case DLL_PROCESS_ATTACH:
            // attach to process
            // return FALSE to fail DLL load
            break;

        case DLL_PROCESS_DETACH:
            // detach from process
            break;

        case DLL_THREAD_ATTACH:
            // attach to thread
            break;

        case DLL_THREAD_DETACH:
            // detach from thread
            break;
    }
    return TRUE; // succesful
}
 

//import com.sun.jna.Library; cdecl call調用約定
import com.sun.jna.Native;
import com.sun.jna.Platform;
import com.sun.jna.win32.StdCallLibrary;

public class main {

    public interface CLibrary extends StdCallLibrary { //cdecl call調用約定時為Library
        CLibrary INSTANCE = (CLibrary)Native.loadLibrary("forjava",CLibrary.class);
        public int add(int a,int b);
    }

    public static void main(String[] args) {
        System.out.print(CLibrary.INSTANCE.add(2,3));
    }
}