1. Calendar类型转化为Date类型和long类型

Calendar calendar=Calendar.getInstance();
Date date=calendar.getTime();
long time=calendar.getTimeInMillis();

2.Date类型转化为Calendar类型和long类型

Date date=new Date(System.currentTimeMillis()+100000000);
Calendar calendar=Calendar.getInstance();
calendar.setTime(date);
long time=date.getTime();

3. long类型转化为Date类型和Calendar类型

long time=System.currentTimeMillis()+100000000;
Date date=new Date(time);
Calendar calendar=Calendar.getInstance();
calendar.setTimeInMillis(time);

Calendar、Date、long类型的时间，三者之间如何转化