Java中的Calendar和Date之间的转换

1、Calendar转换成Date

Calendar cal = Calendar.getInstance();
Date date = cal.getTime;

2、Date转换成Calendar

Date date = new Date();
Calendar cal = Calendar.getInstance();
Cal.setTime(date );

3、当前时间加减小时（年，月，日，小时，分钟）

String oneHoursAgoTime="";
Date dt = new Date();
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd-HH");
Calendar rightNow = Calendar.getInstance();
rightNow.setTime(dt);
//rightNow.add(Calendar.DATE, -1);
rightNow.add(Calendar.HOUR, -1);
Date dt1=rightNow.getTime();
oneHoursAgoTime = sdf.format(dt1);
return oneHoursAgoTime;