java 获取当天（今日）零点零分零秒详解编程语言

                Calendar calendar = Calendar.getInstance(); 
                calendar.setTime(new Date()); 
                calendar.set(Calendar.HOUR_OF_DAY, 0); 
                calendar.set(Calendar.MINUTE, 0); 
                calendar.set(Calendar.SECOND, 0); 
                Date zero = calendar.getTime();

                long current = System.currentTimeMillis(); 
                long zero = current/(1000*3600*24)*(1000*3600*24) - TimeZone.getDefault().getRawOffset();

public static void main(String[] args) { 
        long current=System.currentTimeMillis();//当前时间毫秒数 
        long zero=current/(1000*3600*24)*(1000*3600*24)-TimeZone.getDefault().getRawOffset();//今天零点零分零秒的毫秒数 
        long twelve=zero+24*60*60*1000-1;//今天23点59分59秒的毫秒数 
        long yesterday=System.currentTimeMillis()-24*60*60*1000;//昨天的这一时间的毫秒数 
        System.out.println(new Timestamp(current));//当前时间 
        System.out.println(new Timestamp(yesterday));//昨天这一时间点 
        System.out.println(new Timestamp(zero));//今天零点零分零秒 
        System.out.println(new Timestamp(twelve));//今天23点59分59秒 
}