String，Date，Long三种类型之间相互转换

字符串转化成时间类型（字符串可以是任意类型，只要和SimpleDateFormat中的格式一致即可） 通常我们取时间跨度的时候，会substring出具体时间－－long－比较

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String–>Date–>Long

SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd hh:mm:ss a"); Date date = sdf.parse("2016/11/18 10:31:37 AM");//String-->Date Long dateLong = date.getTime();//Date-->Long

Long–>Date–>String

Long long = 1654651313; Date date = java.sql.Date.valueOf(long);//Long-->Date Date date = new Date(long);//Long-->Date（常用） SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String string=sdf.format(date);//Date-->String

Calendar–>Date–>Calendar

Calendar calendar = Calendar.getInstance(); Date date = calendar.getTime();//calendar-->Date calendar.setTime(date);//Date-->calendar

注意：calendar可以将日期加1

Calendar calendar = Calendar.getInstance(); calendar.setTime(date); calendar.add(Calendar.DATE,1); Date date1 = calendar.getTime();