package javacodebook.misc.jni_date;

import java.util.*;
/**
 * Eine Klasse Date, bei der das Datum gesetzt werden kann
 */
public abstract class SystemClock {

    /**
     * Instanz der Klasse in Abhängig vom Betriebssystem
     * erzeugen.
     */
    public static SystemClock getInstance() throws UnsupportedOperationException {
        String os = System.getProperty("os.name");
        System.out.println(os);
        if (os.toLowerCase().startsWith("windows"))
            return new WinClock();
        else
            throw new UnsupportedOperationException("Unsupported OS!");
    }

    /**
     * Das Datum neu setzen.
     */
    public void resetClock(java.util.Date date) {
        Calendar cal = new GregorianCalendar();
        cal.setTime(date);
        int year   = cal.get(Calendar.YEAR);
        int month  = cal.get(Calendar.MONTH)+1;
        int day    = cal.get(Calendar.DAY_OF_MONTH);
        int hour   = cal.get(Calendar.HOUR_OF_DAY);
        int minute = cal.get(Calendar.MINUTE);
        int second = cal.get(Calendar.SECOND);
        resetClockImpl(year, month, day, hour, minute, second);
    }

    /**
     Die - betriebssystem-abhängige - Methode zum Setzen des Datums
     */
    public abstract void resetClockImpl(int year, int month,  int day,
                                      int hour, int minute, int second);
}

--- Neue Klasse ---

package javacodebook.misc.jni_date;

/**
 * Die Implementation der Klasse SystemClock
 * für Windows-Plattformen
 */
public class WinClock extends SystemClock {

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

    public native void resetClockImpl(int year, int month,  int day,
                                      int hour, int minute, int second);
}

--- Neue Klasse ---

package javacodebook.misc.jni_date;

import java.util.Date;

/**
 * Benutzung der Klasse SystemClock
 */
public class Starter {

    public static void main(String[] args) {

        // Eine Instanz der Klasse SystemClock holen und
        // damit die System-Uhrzeit neu setzen
        SystemClock clock = SystemClock.getInstance();
        Date date = new Date(System.currentTimeMillis()+10000*60);
        clock.resetClock(date);
    }
}

--- Generierte Header-Datei ---

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class javacodebook_misc_jni_0005fdate_WinClock */

#ifndef _Included_javacodebook_misc_jni_0005fdate_WinClock
#define _Included_javacodebook_misc_jni_0005fdate_WinClock
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     javacodebook_misc_jni_0005fdate_WinClock
 * Method:    resetClockImpl
 * Signature: (IIIIII)V
 */
JNIEXPORT void JNICALL Java_javacodebook_misc_jni_1date_WinClock_resetClockImpl
  (JNIEnv *, jobject, jint, jint, jint, jint, jint, jint);

#ifdef __cplusplus
}
#endif
#endif

--- C-Implementation der Funktionalität ---

#include <windows.h>
#include <javacodebook_misc_jni_0005fdate_WinClock.h>

JNIEXPORT void JNICALL Java_javacodebook_misc_jni_1date_WinClock_resetClockImpl
  (JNIEnv *env, jobject obj, jint year, jint month, jint day, jint hour, jint minute, jint second)
{
  SYSTEMTIME tmp;
  SYSTEMTIME *sysTime;

  sysTime          = &tmp;
  sysTime->wYear   = year;
  sysTime->wMonth  = month;
  sysTime->wDay    = day;
  sysTime->wHour   = hour;
  sysTime->wMinute = minute;
  sysTime->wSecond = second;

  SetSystemTime(sysTime);
}