LocalDateTime的增加和减少

1、计算两个LocalDateTime之间的相差的天数

//指定一个字符串时间
String  wordGameStartTime ="2019-01-25 00:00:01";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern( "yyyy-MM-dd HH:mm:ss" );
LocalDateTime dateTime = LocalDateTime.parse(wordGameStartTime,formatter);
//获取当前时间
LocalDateTime now = LocalDateTime.now();  //2019-1-31
int days= (int)Duration.between(dateTime,now).toDays();
System.out.println(days);   //6 

2、LocalDate的减少指定的天数、年数等

LocalDate localDate = LocalDate.now();   //  2019-01-31
//计算去年
LocalDate previousYear = localDate.minus( 1, ChronoUnit.YEARS );   // 2018-01-31
//减30天
LocalDate previousDay = localDate.minus( 30, ChronoUnit.DAYS );  //2019-01-01
//减少6天
LocalDate startTime = localDate.minusDays( 6 ) ; 2019-01-25

3、LocalDate计算上周日的日期

LocalDate localDate = LocalDate.now();//当前日期
int week = localDate.getDayOfWeek().getValue();  //计算今天是星期几
LocalDate endTime = localDate.minusDays( week ); //计算上周日的日期