| 本文记录了一些Java8中新增的日期和时间API的基本用法
1.计算时间间隔
Java8之前，我们想要确定一个方法的运行时间长度，可以这样： - long start = System.currentTimeMillis();
- doSomething();
- long end = System.currentTimeMillis();
- System.out.println(end-start);
Java8中，可以这样 - Instant start = Instant.now();
- doSomething();
- Instant end = Instant.now();
- Duration time = Duration.between(start, end);
- long seconds = time.getSeconds();//秒表示
- long millis = time.toMillis();//毫秒表示
- System.out.println(seconds);
- System.out.println(millis);
可以轻松选择用纳秒、毫秒、秒、分钟、小时或者天来表示时间间隔的单位。
可以这样来比较第一个方法是不是比第二个执行得更快： - Instant start = Instant.now();
- doSomething();
- Instant end = Instant.now();
- Duration time = Duration.between(start, end);
- Instant start2 = Instant.now();
- doSomething2();
- Instant end2 = Instant.now();
- Duration time2 = Duration.between(start2, end2);
- boolean fast = time.minus(time2).isNegative();
- System.out.println(fast);
2.本地日期和时间
- LocalDate now = LocalDate.now();
- LocalDate date = LocalDate.of(2005, 5, 10);
- LocalDate date2 = LocalDate.of(2003, Month.FEBRUARY, 5);
- System.out.println(now);
- System.out.println(date);
- System.out.println(date2);
-
- LocalTime now2 = LocalTime.now();
- LocalTime time = LocalTime.of(22, 50, 56);
- System.out.println(now2);
- System.out.println(time);
3.日期格式化
- //按照内置的不同方式格式化
- String format = DateTimeFormatter.ISO_LOCAL_DATE.format(LocalDate.now());
- String format2 = DateTimeFormatter.ISO_LOCAL_TIME.format(LocalTime.now());
- String format3 = DateTimeFormatter.ISO_DATE.format(LocalDateTime.now());
- String format4 = DateTimeFormatter.ISO_INSTANT.format(Instant.now());
- System.out.println(format);
- System.out.println(format2);
- System.out.println(format3);
- System.out.println(format4);
-
- //按照标准格式格式化
- DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.FULL);
- String format5 = formatter.format(LocalDateTime.now());
- System.out.println(format5);
-
- //按照指定方式格式化
- DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd E HH:mm:ss");
- String format6 = pattern.format(LocalDateTime.now());
- System.out.println(format6);
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