Using windows(c++) functions in java

Using windows(c++) functions in java

I used to program in c++(Windows Programming). In that time controlling
the system was easy. But now when I have changed to java it seems
different. Please help me with a method to use windows functions like ""
in java.
I found something like this C-JNI wrapper, but I dont know how to use it..
I would like to get this code in it :
SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM) 2);
The c++ code looks like this:
#include <windows.h>
int main()
{
SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM) 2);
return 0;
}