求某一日是周几

来源：互联网发布：centos安装oracle11g 编辑：程序博客网时间：2024/05/16 00:30

package com.yenange.test;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class TestWeekDay {
    public static void main(String[] args) throws ParseException {
        String[] weekArr={"周日","周一","周二","周三","周四","周五","周六"};
        String str="2010-10-3";
        System.out.println("求"+str+"是周几?");
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        Date date1=sdf.parse("0001-1-1");
        Date date2=sdf.parse(str);
        System.out.println("第一种方法:用Date.getDay()");
        System.out.println(weekArr[date2.getDay()]);
        System.out.println("第二种方法:用Calendar.get(Calendar.DAY_OF_WEEK)");
        Calendar c=Calendar.getInstance();
        c.setTime(date2);
        System.out.println(weekArr[c.get(Calendar.DAY_OF_WEEK)-1]);
        System.out.println("第三种方法:计算出天数差,模7取余");
        System.out.println(weekArr[(differ(date1, date2).intValue()%7)]);
    }
    public static Long differ(Date date1, Date date2){
        //return date1.getTime() / (24*60*60*1000) - date2.getTime() / (24*60*60*1000);
        return date2.getTime() / 86400000 - date1.getTime() / 86400000; //用立即数，减少乘法计算的开销
    }
}