Java时间相关问题

long t=System.currentTimeMillis();

Date date = new Date();
long t=System.currentTimeMillis();
date.setTime(t);
System.out.println(date);

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH-mm-ss");
String fmDate=simpleDateFormat.format(new Date());

String sdate = "2020-06-01 06-06-06";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH-mm-ss");
long time = simpleDateFormat.parse(sdate).getTime();

Date date=new Date();
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String fmDate=simpleDateFormat.format(date);