完善例题3.2的日期类mydate

package mydate;

public class mydate {
private int year,month,day;
private static int thisYear;

static
{thisYear=2012;}
public mydate(int year,int month,int day)
{ this.set(year,month,day);}
public mydate()
{ this(1970,1,1);}
public mydate(mydate d)
{ this.set(d);}
public void set(int year,int month,int day)
{
this.year=year;
this.month=(month>=1&&month<=12)?month:1;
this.day=(day>=1&&day<=31)?day:1;
}
public void set(mydate d)
{ set(d.year,d.month,d.day);}
public int getYear()
{ return this.year;}
public int getMonth() {return this.month;}
public int getDay() {return this.day;}
public String toString()
{ return year+"年"+String.format("%02d",month)+"月"+String.format("%02d",day)+"日";}
public static int getThisYear()
{ return thisYear;}
public static boolean isLeapYear(int year)
{ return year%400==0||year%100!=0&&year%4==0;}
public boolean equals(mydate d)
{ return this==d||d!=null&&this.day==d.year&&this.month==d.month&&this.day==d.day;}
public static int daysOfMonth(int year,int month)
{
switch(month)
{ case 1:case 3:case 5:case 7:case 8:case 10:case 12: return 31;
case 4:case 6:case 9:case 11: return 30;
case 2: return mydate.isLeapYear(year)?29:28;
default: return 0;
}
}
public int daysOfMonth()
{ return daysOfMonth(this.year,this.month);}
public void tomorrow()
{
this.day++;
if(this.day>this.daysOfMonth())
{
this.day=1;
this.month++;
if(this.month>12)
{this.month=1;
this.year++;}
}

}
public mydate yestoday()
{
mydate date=new mydate(this);
date.day--;
if(date.day==0)
{
date.month--;
if(date.month==0)
{ date.month=12; date.year--;}
date.day=daysOfMonth(date.year,date.month);
}
return date;
}

}
class mydate_ex
{
public static void main(String args[])
{
System.out.println("今年是"+mydate.getThisYear()+
",闰年?"+mydate.isLeapYear(mydate.getThisYear()));
mydate d1=new mydate(2012,12,31);
mydate d2=new mydate(d1);
System.out.println("d1:"+d1+",d2:"+d2+",d1==d2?"+(d1==d2)+",d1.equals(d2)?"+d1.equals(d2));
System.out.print(d1+"的明天是");
d1.tomorrow();
System.out.println(d1+"\n"+d1+"的昨天是"+(d2=d1.yestoday()));
}

}