jdk1.8时间处理

jdk1.8 

// 时间转字符串  20181205001404
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmss");
System.out.println(dateTimeFormatter.format(LocalDateTime.now()));

// 字符串转时间  2018-12-05T00:14:04
TemporalAccessor temporalAccessor = dateTimeFormatter.parse("20181205001404");
System.out.println(LocalDateTime.from(temporalAccessor));

// 获取当前年份 2018-12-05
System.out.println(LocalDate.now());
// 获取当前时间 00:14:04.443
System.out.println(LocalTime.now());
// 当前年月日时分秒 2018-12-05T00:14:04.443
System.out.println(LocalDateTime.now());

// 毫秒值 1543940044443
System.out.println(Clock.systemDefaultZone().millis());

jdk1.7

// 毫秒值转日期
long currentMillis = System.currentTimeMillis();
DateFormat df = new SimpleDateFormat("yyyy-hh-dd HH:mm:ss");
Date date = new Date();
date.setTime(currentMillis);
String currentDate = df.format(date);
System.out.println(currentDate);
注：date对象也可以使用Calendar类获取
    Calendar c = Calendar.getInstance();
    c.setTimeInMillis(currentMillis); 
    Date date = c.getTime();

// 日期字符串转毫秒值
DateFormat df = new SimpleDateFormat("yyyy-hh-dd HH:mm:ss");
String dateStr = "2017-11-01 23:18:37";
long dateMillis = df.parse(dateStr).getTime();
System.out.println(dateMillis);