Calendar（抽象类）日历类的使用

代码如下：

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

public class StartApplication {
    public static void main(String[] args) {

        //1.实例化
        //方式一:创建其子类(Gregoriancalendar)的对象/方式二:调用其静态方法getInstance( )
        Calendar calendar = Calendar.getInstance();
        System.out.println(calendar.getClass());//class java.util.GregorianCalendar

        //常用方法
        //get()
        int month = calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(month);
        System.out.println(calendar.get(Calendar.DAY_OF_YEAR));

        //set()
        calendar.set(Calendar.DAY_OF_YEAR, 100);
        System.out.println(calendar.get(Calendar.DAY_OF_YEAR));

        //add()
        calendar.add(Calendar.DAY_OF_YEAR, 10);
        System.out.println(calendar.get(Calendar.DAY_OF_YEAR));

        //getTime()：日历类-->Date类
        Date time = calendar.getTime();
        System.out.println(time);

        //setTime()：Date类-->日历类
        calendar.setTime(new Date());
        System.out.println(calendar.get(Calendar.DAY_OF_YEAR));

    }
}

结果：

class java.util.GregorianCalendar
10
130
100
110
Wed Apr 20 14:42:06 CST 2022
130