关于Calendar的常用方法练习1

 

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

    
public class DateUtil {
    static Calendar ca = Calendar.getInstance();
    /**
     *1 将Date转换为String
     * @return
     */
    public static void getDateToString(){
        Date a = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("y-M-d");
        String str = sdf.format(a); 
        System.err.println(str);
    }
    /**
     *2 将String日期转换为Date
     * @param str
     * @return
     */
    public static Date getStringToDate(String str){
        SimpleDateFormat sdf = new SimpleDateFormat("y-M-d");
        Date date=null;
        try {
            date = sdf.parse(str);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally{
        System.err.println(date);
        return date;
        }
    }
    /**
     *3 计算该月份最多有多少天
     * @param year
     * @param month
     * @return
     */
    public static int getMaximumDay(int year,int month){
        Date now = new Date();
        
         ca.clear();
         ca.set(Calendar.YEAR,year);
         ca.set(Calendar.MONTH,month-1);
         //ca.set(Calendar.DATE,day);
        int a = ca.getActualMaximum(Calendar.DAY_OF_MONTH);
        System.out.println(a);
        return a ;
    }
    /**
     *4 指定日期计算这是当年第几天第几星期
     * 
     * @param str
     */
    public static void setDate(String str) {
        SimpleDateFormat sdf = new SimpleDateFormat("y-M-d");
        Date date = null;
        try {
            date = sdf.parse(str);
            ca.clear();
            ca.setTime(date);
            int a = ca.get(Calendar.DAY_OF_YEAR);
            int b = ca.get(Calendar.WEEK_OF_YEAR);
            System.err.println("此日期为当年的第"+a+"天"+"第"+b+"周");

        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    /**
     *5 计算一年中第几个星期天是几号：
     * @param args
     */
    public static void getDate(int year,int week){
        ca.clear();
        ca.set(Calendar.YEAR, year);
        ca.set(Calendar.WEEK_OF_YEAR, week);
        ca.set(Calendar.DAY_OF_WEEK,Calendar.SUNDAY);
        SimpleDateFormat sdf = new  SimpleDateFormat();
        int m = ca.get(Calendar.DAY_OF_MONTH);
        int n = ca.get(Calendar.MONTH);
        System.out.println(sdf.format(ca.getTime()));
    }
    /**
     *6 将日历转换为日期
     */
    public static void getCalendarToDate(){
        ca.getTime();
        System.out.println(ca.getTime());
    }
    /**
     *7 将日期转换为日历
     */
    public static void getDateToCalendar(){
        Date now = new Date();
        ca.setTime(now);
        ca.getCalendarType();
        System.out.println(ca);
      //  System.out.println(ca.getCalendarType());
    }
    /**
     *8 计算两个日期相隔多少天
     * @param date1
     * @param date2
     */
    public static void getDays(String date1,String date2){
        ca.setTime(getStringToDate(date1));
        int a1 = ca.get(Calendar.DAY_OF_YEAR);
        ca.setTime(getStringToDate(date2));
        int a2 = ca.get(Calendar.DAY_OF_YEAR);
        System.err.println("同年两个日期的相隔的天数为："+Math.abs(a2-a1));
    }
　　　　
    public static void main(String[] args) {
        // TODO Auto-generated method stub
//        getDateToString(); //1,将Date的日期转化为String的形式返回
//        getStringToDate("2018-09-12");//2.将String类型转成
//        getMaximumDay(2017,2);//3.指定年份和月份,计算该月份最大有多少天Date类型
//        setDate("2018-09-26");//4.指定日期，计算该天是当年第多少天，多个个星期
//        getDate(2018,2);//5.计算一年中的第几星期天是几号
//        getDateToCalendar();//6.Date类型转成Calendar
//        getCalendarToDate();//7.Calendar类型转成Date
//        getDays("2018-08-01","2018-09-1");//8.计算两个同一年的时间中间相隔的天数
    }

}