date.java

Java程序设计(美) David D. Riley著 机械工业出版社 书籍配套 代码

// Figure 9.21

public abstract class Date  {
	protected int day;  	// day within a month
	protected Month month;  
	protected int year;   // full calendar year (A.D.)

	/**	pre:	1 <= m <= 12
	 *			and  d is a sensible day for month m
	 *				(Note that this method doesn't check date validity) <br>
	 *	post:	day == d  and  month == m  and  year == y  
	 */
    public Date( int d, Month m, int y )  {
    	day = d;
    	month = m;
    	year = y;
    }

	/**	post:	result is the last two digits of year  */
	public String twoDigitYear()   {
		return "" + year % 100;
	}

	/**	post:	result is some appropriate string form of the date  */
	public abstract String dateString();
    
	/**	post:	result is the month name followed by day coma year */
    public String toString()   {
		return "" + month.name() + " " + day + ", " + year;
	}
    
    public boolean equals( Object z )   {
		return 
			z instanceof Date
			&& day == ((Date)z).day  
			&&  month == ((Date)z).month  
			&&  year == ((Date)z).year;
	}


}