1.Date 转化Calendar
Calendar calendar = Calendar.getInstance();
calendar.setTime(new Date());
2.Calendar转化Date
Calendar calendar = Calendar.getInstance();
Date date =calendar.getTime();
3.Calendar 转化 String
Calendar可获取当前时间的具体情况,如年，月，日，时，分，秒，周，月内第几天等。
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.DAY,-1);//昨天
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
String dateStr = sdf.format(calendar);
4.String 转化Calendar
String str="2017-5-17";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date =sdf.parse(str);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
5.Date 转化String
SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd");
String dateStr=sdf.format(new Date());
6.String 转化Date
String str="2017-5-17";
SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd");
Date date = sdf.parse(str);
7.date转化int
long nowTime = System.currentTimeMillis()/1000;
Integer nowTimeInt = new Long(nowTime).intValue();
8.int转化date
long nowTimeLong=new Long(nowTimeInt).longValue()*1000;
DateFormat ymdhmsFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String nowTimeStr = ymdhmsFormat.format(nowTimeLong);
