大神求助《properties.load(fileInputStream )》java.lang.NullPointerException

我明明把配置文件路径给对了，可是总是说空指针异常。查了一下午还没有弄明白。求大神解救。。。调试总是显示在 properties.load(fileInputStream );出现异常。。
代码如下：
public Configuration () throws FileNotFoundException
{

try {

        File file=new File(fPath.CONF_PATH);
        fileInputStream =new FileInputStream(file);
        System.out.println (fPath .CONF_PATH );
        properties.load(fileInputStream );
        fileInputStream .close();
    } catch (IOException e) {
        System.out.println ("Can not find the configuration file");
        e.printStackTrace();
    }
}

获取文件路径的代码如下；
public static String realpath = File_Path.class.getClassLoader().getResource("/").toString();
public String path = realpath.substring(realpath.indexOf("file:/") + 6, realpath.indexOf("WEB-INF")).replaceAll("%20", " ");
public String CONF_PATH=path+"conf/conf.properties";