java中获取一天当中的毫秒数

Long s=System.currentTimeMillis();
  Date date=new Date();
   SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-HH hh:mm:ss");
   System.out.println(s);
  Calendar c = Calendar.getInstance();
  c.set(Calendar.HOUR_OF_DAY, 0);
  c.set(Calendar.MINUTE, 0);
  c.set(Calendar.SECOND, 0);
  Date m6 = c.getTime();
  long a=m6.getTime();
  System.out.println(m6.getTime());
 
 
  Calendar c1 = Calendar.getInstance();
  c1.set(Calendar.HOUR_OF_DAY, 24);
  c1.set(Calendar.MINUTE, 0);
  c1.set(Calendar.SECOND, 0);
  Date m7 = c1.getTime();
  long b=m7.getTime();
  System.out.println(b);
  if(s>=a&&s<b){
    System.out.println(123);