import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class Demo01 {
    public static void main(String[] args) {
        Calendar calendar = new GregorianCalendar();
        System.out.println("calendar:::" + calendar);//
        System.out.println("年：" + calendar.get(Calendar.YEAR));//年
        System.out.println("月：" + calendar.get(Calendar.MONTH));//月
        System.out.println("日：" + calendar.get(Calendar.DATE));//日
        System.out.println("日：" + calendar.get(Calendar.DAY_OF_MONTH));//日
        System.out.println("时：" + calendar.get(Calendar.HOUR));//时
        System.out.println("分：" + calendar.get(Calendar.MINUTE));//分

        calendar.set(Calendar.YEAR,2020);//设置年
        System.out.println("年：" + calendar.get(Calendar.YEAR));//年
        System.out.println("当月的最大天数:"+calendar.getActualMaximum(Calendar.DAY_OF_MONTH));//当月的最大天数


        //Date和Calendar之间的转换
        Date date = new Date();
        Calendar calendar1= new GregorianCalendar();
        calendar1.setTime(date);//Date类转为日历类
        System.out.println("Date类转为日历类："+date);
        Date time = calendar1.getTime();//日历类转为Date类
        System.out.println("日历类转为Date类："+time);
    }
}

//运行结果：

calendar:::java.util.GregorianCalendar[time=1626356605671,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=19,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2021,MONTH=6,WEEK_OF_YEAR=29,WEEK_OF_MONTH=3,DAY_OF_MONTH=15,DAY_OF_YEAR=196,DAY_OF_WEEK=5,DAY_OF_WEEK_IN_MONTH=3,AM_PM=1,HOUR=9,HOUR_OF_DAY=21,MINUTE=43,SECOND=25,MILLISECOND=671,ZONE_OFFSET=28800000,DST_OFFSET=0]
年：2021
月：6
日：15
日：15
时：9
分：43
年：2020
当月的最大天数:31
Date类转为日历类：Thu Jul 15 21:43:25 CST 2021
日历类转为Date类：Thu Jul 15 21:43:25 CST 2021

Process finished with exit code 0