java_日历类

calendar是日历类，该类是抽象类不能被实例化

 public class CalendarTest {
     /*
     创建对象和方法的使用
      */
     public static void main(String[] args) {
         //实例化对象
         Calendar instance = Calendar.getInstance();
         //说明是子类实现class java.util.GregorianCalendar
         System.out.println(instance.getClass());
         //get方法得到本月的日
         int day = instance.get(Calendar.DAY_OF_MONTH);
         System.out.println(day);
         //set设置日为10
         instance.set(Calendar.DAY_OF_MONTH,10);
         int day1 = instance.get(Calendar.DAY_OF_MONTH);
         System.out.println(day1);
         //add添加3天
         instance.add(Calendar.DAY_OF_MONTH,3);
         int day2 = instance.get(Calendar.DAY_OF_MONTH);
         System.out.println(day2);
         //把日历类转换为date
         Date time = instance.getTime();
         System.out.println(time);
         //把date转为日历
         Date date = new Date();
         instance.setTime(date);
         int i = instance.get(Calendar.DAY_OF_MONTH);
         System.out.println(i);
     }
 }