日期时间转换

 java8各种时间转换：

1、long(时间戳) to localDateTime

private LocalDateTime parsingTimestamp(long timestamp) {
　　//return (new Timestamp(timestamp)).toLocalDateTime()
    return LocalDateTime.ofInstant(ofEpochMilli(timestamp), systemDefault());
}

 2、long(时间戳) to 格式化时间字符串

private static final DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");

private static final DateTimeFormatter dtf_bak = DateTimeFormatter.ofPattern("yyyy-MM-dd");

String dateTime = dtf.format(LocalDateTime.ofInstant(Instant.ofEpochMilli(long 毫秒时间戳), ZoneId.systemDefault()));

String date = dtf_bak.format(LocalDateTime.ofInstant(Instant.ofEpochMilli(json.getLong("log_timestamp")), ZoneId.systemDefault())); 

 3、把指定字符串格式化为日期

String str1="2018-07-05 12:24:12";
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime parse = LocalDateTime.parse(str1, dtf);
System.out.println(parse);

 4、时间转字符串字符串转时间

DateTimeFormatter f = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
//时间转为字符串
LocalDateTime date =LocalDateTime.now();
String str = date.format(f);  // 2014-11-07 14:10:36
//字符串转为时间
date = LocalDateTime.parse(str,f); 

 more ：https://blog.csdn.net/u012843361/article/details/80496272

Joda-Time各种时间转换：

/**
     * 获取系统当前时间按照指定格式返回
     * 
     * @param pattern yyyyMMddHHmmssSSS
     * @return
     */
    public static String getCurrentTimePattern(String pattern) {
        DateTime dt = new DateTime();
        String time = dt.toString(pattern);
        return time;
    }