完善【例3.2】

public class MyDate //公有的类，与源程序文件同名
{
private int year,month,day;//私有成员变量
private static int thisYear;//私有静态成员变量
static
{
thisYear=2012;//静态成员变量初始化
}
public MyDate(int year,int month,int day)//构造方法，指定日期
{
this.set(year,month,day);
}
public MyDate()//无参数构造方法，重载指定默认日期
{
this(1970,1,1);
}
public MyDate(MyDate d)//重载，拷贝构造方法
{
this.set(d);
}
public void set(int year,int month,int day)//设置日期
{
this.year=year;//this.year指当前对象的成员变量
this.month=(month>=1&&month<=12)?month:1;
this.day=(day>=1&&day<=31)?day:1;
}
public void set(MyDate d)//设置日期，重载
{
set(d.year,d.month,d.day);
}
public int getYear()//获得年份
{
return this.year;
}
public int getMonth()//获得月份
{
return this.month;
}
public int getDay(){//获得日期
return this.day;
}
public String toString(){//返回中文日期字符串
return year+"年"+String.format("%02d",month)+"月"+String.format("%02d",day)+"日";
}
public static int getThisYear()//获得年份
{
return thisYear;//访问静态成员变量
}
public static boolean isLeapYear(int year)//判断是否是闰年，静态方法
{
return year%400==0||year%100!=0&&year%4==0;
}
public boolean isLeapYear()//判断当前年份是否为闰年

{
return isLeapYear(this.year);
}
public boolean equals(MyDate d)
{
return this==d||d!=null&&this.year==d.year&& this.month==d.month &&this.day==d.day;
}
public static int daysOfMonth(int year,int month)
{
switch(month)//计算每月的天数
{
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()//返回当月天数
{
return daysOfMonth(this.year,this.month);
}
public void tomorrow()//当前日期改为后一天日期
{
this.day++;
if(this.day>this.daysofMonth())
{
this.day=1;
this.month++;
if(this.month>12)
{
this.month=1;
this.year++;
}
}
}
public MyDate yestoday()//当前日期前一天日期
{
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//当包中的其他类，缺省权限
{
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()));
}

}