moneyusa.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 6.7

/**	Class	Invariant
 *	A MoneyUSA object maintains a monetary amount as an integer count of
 *	dollars, quarters, dimes, nickels, and pennies and dollars>=0
 *	and  quarters>=0  and  dimes>=0 and nickels>=0  and  pennies>=0  
 */
public class MoneyUSA  {
	public  int  dollars;
	public  int  quarters;
	public  int  dimes;
	public  int  nickels;
	public  int  pennies;
    
	/**	pre:	dol>=0  and  q>=0  and  di>=0  and  n>=0  and  p>=0  <br>
	 *	post:	dollars == dol  and  quarters == q  and  dimes == di
	 *			and  nickels == n  and  pennies == p   
	 */
	public  MoneyUSA(int dol, int q, int di, int n, int p)   {
		dollars = dol;
		quarters = q;
		dimes = di;
		nickels = n;
		pennies = p;
	} 

	/**	post:	result == dollars*100+quarters*25+dimes*10+nickels*5+pennies */
	public  int  valueInCents()  {
		return dollars*100+quarters*25+dimes*10+nickels*5+pennies;			
	}

	/**	post:	result == (dollars*100+quarters*25+dimes*10+nickels*5+pennies)/100 */
	public  double  valueInDollars()  {
		return valueInCents() / 100.0;
	}

	/**	post:	valueInCents() == valueInCents()@pre  and  0<=pennies<=4
	 *			and  0<=nickels<=1  and  0<=dimes<=2  and  0<=quarters<=3 
	 */
	public  void  consolidate()   { 
		int  remainingCents = valueInCents();
		dollars = remainingCents / 100;
		remainingCents = remainingCents % 100;
		quarters = remainingCents / 25;
		remainingCents = remainingCents % 25;
		dimes = remainingCents / 10;
		remainingCents = remainingCents % 10;
		nickels = remainingCents / 5;
		pennies = remainingCents % 5;
	}
}