JAVA中的一些工具类的使用

1.Calendar日历类

Calendar rightNow = Calendar.getInstance();
        log.error("日历输出:{}-{}-{}-{}-{}",rightNow.get(Calendar.YEAR),rightNow.get(Calendar.MONTH),
            rightNow.get(Calendar.DATE),rightNow.get(Calendar.HOUR_OF_DAY),rightNow.get(Calendar.AM_PM)); // 0为上午

        rightNow.add(Calendar.YEAR,5);
        log.error("年份:{}",rightNow.get(Calendar.YEAR));
        log.error("时间:{}",rightNow.getTime());
        log.error("时间2:{}",rightNow.getTime().getTime());

输出：

2021-02-19 09:44:50.043 ERROR 756 --- [           main] docker.demo.DemoApplication              : 日历输出:2021-1-19-9-0
2021-02-19 09:44:50.043 ERROR 756 --- [           main] docker.demo.DemoApplication              : 年份:2026
2021-02-19 09:44:50.044 ERROR 756 --- [           main] docker.demo.DemoApplication              : 时间:Thu Feb 19 09:44:50 CST 2026
2021-02-19 09:44:50.044 ERROR 756 --- [           main] docker.demo.DemoApplication              : 时间2:1771465490043

真实时间是2021-2-19 09:47，月份是从0开始的，所以需要+1，rightNow.add可以在原有时间上添加相应的时间