java记录之Date的使用

import java.time.LocalDate;
import java.time.Period;
import java.util.Calendar;
import java.math.*;
public class demo {
     demo(){
         
     }
     public void demo1(int y,int m,int d){
         System.out.println("下一天是"+y+"年"+m+"月"+(d+1)+"日");
     }
     public void demo2(int y,int m,int d) {
         Calendar cl = Calendar.getInstance();
         cl.set(y,m-1,d);
        int w = cl.get(Calendar.DAY_OF_WEEK);
         switch(w) {
         case 1:System.out.println("星期日");break;
         case 2:System.out.println("星期一");break;
         case 3:System.out.println("星期二");break;
         case 4:System.out.println("星期三");break;
         case 5:System.out.println("星期四");break;
         case 6:System.out.println("星期五");break;
         case 7:System.out.println("星期六");break;
         }             
     }
    public void demo3(int y1,int m1,int d1,int y2,int m2,int d2) {
        LocalDate today = LocalDate.of(y1, m1, d1);
        System.out.println("Today：" + today);
        LocalDate oldDate = LocalDate.of(y2, m2, d2);
        System.out.println("OldDate：" + oldDate);
        Period p = Period.between(oldDate, today);
        System.out.printf("目标日期距离今天的时间差：%d 年 %d 个月 %d 天
", p.getYears(), p.getMonths(), p.getDays());
        
    }
    public void demo4(BigInteger m1,BigInteger m2) {
        BigInteger result = new BigInteger("0");
        result = m1.add(m2);
        System.out.println("和为"+result);
        result = m1.multiply(m2);
        System.out.println("乘积为"+result);
        result = m1.subtract(m2);
        System.out.println("差为"+result);
        result = m1.divide(m2);
        System.out.println("商为"+result);
    }
     
}



import java.util.Calendar;
import java.util.*;
import java.math.*;
public class Test3 {
   public static void main(String [] args) {
       Calendar cal = Calendar.getInstance();
       Scanner sc = new Scanner(System.in);
       System.out.println("输入1代表输入一个日期，输出这个日期的下一天
" + 
               "2代表输入一个日期，输出这个日期是星期几
" + 
               "3代表输入两个日期，输出这两个日期之间的天数
" + 
               "4代表输入两个整数（多于20位），输出这两个整数的和、差、积、商
" + 
               "");
       int n = sc.nextInt();     
   demo test = new demo();//输入过程省略
   if(n==1) {
       test.demo1(2010,10,1);
   }
   if(n==2) {
       test.demo2(2010, 10, 1);
   }
   if(n==3) {
       test.demo3(2019, 12, 13, 2018, 3, 12);
   }
   if(n==4) {
       BigInteger m1 = new BigInteger("839472983749234234234234234");
       BigInteger m2 = new BigInteger("85937450924705925892650347");
       test.demo4(m1,m2);
   }
}}