Another problem for your consideration

Another problem for your Another problem for your considerationconsideration

Make changeMake change

Write a program that determines the change to be Write a program that determines the change to be dispensed from a vending machine.dispensed from a vending machine. An item in the machine can cost between 25 An item in the machine can cost between 25

cents and a dollar, in 5-cent increments.cents and a dollar, in 5-cent increments. The machine accepts only a single dollar bill to The machine accepts only a single dollar bill to

pay for the item.pay for the item.

For example, a possible sample dialog might be:For example, a possible sample dialog might be:

Enter price of an item: 45Enter price of an item: 45You bought an item for 45 cents and gave me a You bought an item for 45 cents and gave me a

dollar so your change is:dollar so your change is:2 quarters,2 quarters,0 dimes, and0 dimes, and1 nickel1 nickel

Make changeMake change

Steps in our algorithm:Steps in our algorithm:1.1. Get the price.Get the price.

2.2. Calculate change.Calculate change.

3.3. Report the results.Report the results.

/*/*

File : Change.javaFile : Change.java

Author: G.J. GreveraAuthor: G.J. Grevera

Desc. : Purchase an item and make change.Desc. : Purchase an item and make change.

*/*/

public class Change {public class Change {

public static void main ( String args[] ) {public static void main ( String args[] ) {

//get the price//get the price

//calculate change//calculate change

//report results (change)//report results (change)

}}

}}

Make change v1Make change v1

/*/*




*/*/




int price = 35;int price = 35;


int quarters = 0;int quarters = 0;

int dimes = 0;int dimes = 0;

int nickels = 0;int nickels = 0;


System.out.println( "Bye.“ );System.out.println( "Bye.“ );

}}

}}



//prompt for the price//prompt for the price

System.out.print( "Enter price of an item: " );System.out.print( "Enter price of an item: " );








System.out.println( "You bought an item for " + price +System.out.println( "You bought an item for " + price +

" cents and gave me a dollar so your change is:" );" cents and gave me a dollar so your change is:" );

System.out.println( "\t" + quarters + " quarters,“ );System.out.println( "\t" + quarters + " quarters,“ );

System.out.println( "\t" + dimes + " dimes, and" );System.out.println( "\t" + dimes + " dimes, and" );

System.out.println( "\t" + nickels + " nickels“ );System.out.println( "\t" + nickels + " nickels“ );

}}

















}}


Enter price of an item: You bought an item for 35 cents and gave me a dollar soyour change is: 0 quarters, 0 dimes, and 0 nickels

import java.util.Scanner;import java.util.Scanner;



//get ready to read from the keyboard//get ready to read from the keyboard

Scanner in = new Scanner( System.in );Scanner in = new Scanner( System.in );




int price = int price = in.nextInt()in.nextInt();;











}}

}}


Next, how do we calculate our change?







int price = in.nextInt();int price = in.nextInt();


int change = 100 - price;int change = 100 - price;










}}


How do we calculate the number of quarters in our change?










int quarters = change / 25;int quarters = change / 25;









}}


Ok.How do we calculate the number of dimes in our change?











change = change – quarters * 25;change = change – quarters * 25;









}}


Ok.How do we calculate the number of dimes in our change?












int dimes = change / 10;int dimes = change / 10;








}}


Ok.How do we calculate the number of nickels in our change?













change = change – dimes * 10;change = change – dimes * 10;

int nickels = change / 5;int nickels = change / 5;







}}


Done!

Make change v5 (final)Make change v5 (final)

/*/*




*/*/

import java.util.Scanner;import java.util.Scanner;












change = change - quarters * 25;change = change - quarters * 25;


change = change - dimes * 10;change = change - dimes * 10;





System.out.println( "\t" + quarters + " quarters," );System.out.println( "\t" + quarters + " quarters," );


System.out.println( "\t" + nickels + " nickels" );System.out.println( "\t" + nickels + " nickels" );

}}

}}

Food for thought . . .Food for thought . . .

What message appears if there is What message appears if there is exactly 1 in the change?exactly 1 in the change? 1 quarters1 quarters 1 dimes1 dimes 1 nickels1 nickels

How can we fix this to say ‘1 quarter’ How can we fix this to say ‘1 quarter’ instead?instead?






















}}

How can we fix this to say ‘1 quarter’ instead?

Make change v6Make change v6 public static void main ( String args[] ) {public static void main ( String args[] ) {

. . .. . .



" cents and gave me a dollar so your change " cents and gave me a dollar so your change is:" );is:" );

if (quarters != 1)if (quarters != 1)


elseelse

System.out.println( "\t" + quarters + " quarter," );System.out.println( "\t" + quarters + " quarter," );



}}

How can we fix this to say ‘1 dime’ instead?How can we fix this to say ‘1 nickel’ instead?

More food for thought . . .More food for thought . . .

What happens if someone enters a What happens if someone enters a bad value for the price of an item?bad value for the price of an item? 150150 7272 -50-50






















}}

How can we fix this to output an error message if a value bigger than $1 was entered?








if (price > 100)if (price > 100)

System.out.println( “Price must be less than or equal to System.out.println( “Price must be less than or equal to $1.00“ );$1.00“ );

. . .. . .

But this continues even if a message appears!

As James Brown said, “Can’t go on. Can’t go on.”








if (price > 100) {if (price > 100) {

System.out.println( “Price must be less than or equal to System.out.println( “Price must be less than or equal to $1.00“ );$1.00“ );

System.exit( 0 ); //end program immediatelySystem.exit( 0 ); //end program immediately

}}

. . .. . . Ok.

How about a price less than 0?

How about a price with pennies?

Another problem for your consideration

Documents

Transcript of Another problem for your consideration