Java时间操作

飞熊 • 2024年1月29日下午10:33 • 技术随笔 • 阅读 233

如何取得年月日、小时分钟秒

    /*
    * 三方法：
    *   1. Calender.getInstance()
    *   2. LocalDateTime.now()
    *   3. Clock.systemDefaultZone().mills() 获取时间戳
    * */
    public static void main(String[] args) {
        Calendar instance = Calendar.getInstance();
        /*System.out.println(instance.get(Calendar.YEAR));
        System.out.println(instance.get(Calendar.SECOND));

        LocalDateTime now = LocalDateTime.now();
        System.out.println(now.getYear());
        System.out.println(now.getSecond());*/

        //System.out.println(instance.getTimeInMillis());
        //System.out.println(System.currentTimeMillis());
        System.out.println(Clock.systemDefaultZone().millis());
    }

打印昨天的当前时刻

    public static void main(String[] args) {
        Calendar instance = Calendar.getInstance();
        //这里使用的add方法
        instance.add(Calendar.DATE,-1);
        System.out.println(instance.get(Calendar.DATE));
    }
    //打印昨天的当前时刻
    public static void main(String[] args) {
        LocalDateTime localDateTime = LocalDateTime.now();
        //这里生成了一个新的对象
        LocalDateTime localDateTime1 = localDateTime.minusDays(1);
        System.out.println(localDateTime1.getDayOfMonth());

    }

LocalDate类（新类）

public static void main(String[] args) {
        LocalDate now = LocalDate.now();
        System.out.println(now);

        LocalDate of = LocalDate.of(2014, Month.MAY, 7);
        System.out.println(of);

        LocalDate now1 = LocalDate.now(ZoneId.of("Asia/Kolkata"));
        System.out.println(now1);

        //打印2014年的第100天
        System.out.println(LocalDate.ofYearDay(2014, 100));
        System.out.println(LocalDateTime.now());
        LocalDateTime now = LocalDateTime.of(LocalDate.now(), LocalTime.now());
        System.out.println(now);
    }

LocalDate类常见API：

public static void main(String[] args) {
        //Java8里面的时间API封装的方法
        LocalDate now = LocalDate.now();
        System.out.println(now.minusDays(2));
        System.out.println(now.plusMonths(2));
        System.out.println(now.isLeapYear());
    }

按规定格式解析时间

LocalDate now = LocalDate.now();
System.out.println(now.format(DateTimeFormatter.BASIC_ISO_DATE));

LocalDateTime now1 = LocalDateTime.now();
System.out.println(now1.format(DateTimeFormatter.BASIC_ISO_DATE));

String date = "20201031";
LocalDate now3 = LocalDate.parse(date, DateTimeFormatter.BASIC_ISO_DATE);
System.out.println(now3);