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The Big Programming Thread - Page 251

Forum Index > General Forum
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Thread Rules
1. This is not a "do my homework for me" thread. If you have specific questions, ask, but don't post an assignment or homework problem and expect an exact solution.
2. No recruiting for your cockamamie projects (you won't replace facebook with 3 dudes you found on the internet and $20)
3. If you can't articulate why a language is bad, don't start slinging shit about it. Just remember that nothing is worse than making CSS IE6 compatible.
4. Use [code] tags to format code blocks.
tuho12345
Profile Blog Joined July 2011
4482 Posts
Last Edited: 2013-02-19 02:40:15
February 19 2013 02:15 GMT
#5001
Hi everyone, I'm a newbie in programming and Java specifically. I had a little experience with VB, which is significantly easier than Java or C I guess. So I'm kinda stuck right here and wish I'd have more time but it's due tomorrow and I'm struggling with other exams as well.

Here below is my code, and my question is how can I calculate the SalesTotal and SalesCount. I understand the logic but I have no idea how Java works.
Thanks

+ Show Spoiler +



/**
Assignment 2, CS49J, Spring 2013
Part B student
A cash register totals up sales and computes change due.
*/
public class CashRegister
{
      private double purchase;
      private double payment;

//... Add your code here
      private double SalesTotal;
      private int SalesCount;
/**
Constructs a cash register with no money in it.
*/
public CashRegister()
{
       purchase = 0;
       payment = 0;
      SalesCount = 0;
       SalesTotal = 0;
}

/**
Records the sale of an item.
@param amount the price of the item
*/
public void recordPurchase(double amount)
{
      double total = purchase + amount;
//... Add your code here
       purchase = total;

}

/**
Enters the payment received from the customer.
@param amount the amount of the payment
*/
public void enterPayment(double amount)
{
      payment = amount;
      SalesCount++;
}

/**
Computes the change due and resets the machine for the next customer.
@return the change due to the customer
*/
public double giveChange()
{
      double change = payment - purchase;
      purchase = 0;
       payment = 0;
      return change;
}

/**
Get the total amount of all sales for the day.
@param return sale total
*/
//... Add your code here
public double getSalesTotal()
{

      SalesTotal = purchase + purchase;
      return SalesTotal;

}



/**
Get the total number of sales for the day.
@param return the number of sales.
*/
//... Add your code here

public double getSalesCount()
{
      return SalesCount;
}
/**
Reset counters and totals for the next days sales.
@param none
*/
//... Add your code here
public void reset()
{
      SalesCount = 0;
      payment = 0;
      purchase = 0;
      SalesTotal = 0;
}
}

InRaged
Profile Joined February 2007
1047 Posts
February 19 2013 02:23 GMT
#5002
On February 19 2013 08:37 darkness wrote:
Show nested quote +
On February 19 2013 08:36 Abductedonut wrote:
On February 19 2013 08:28 darkness wrote:
I just want to express my appreciation of how much easier Java is than C. I also think I'm going to ask for help in the near future, haha. At least now I know why my C lecturer asks us to implement only math stuff. His major was math before switching to Computer Science. -.-

Edit: Ok, here's a simple problem.

Input two positive integers a and b (separated by one space). a and b can be very large (up to 99 digits). Output a+b. You are not allowed to use floating-point data types, including float, double, and long double.


Could you give a hint what to use or what to look for? Except for GMP (which may not be accepted by the Online Judge) and floating-point data types.


Keep in mind that your computer can only store 64-bit or 32-bit numbers. Your best bit is to store the numbers in an array and write the addition operation yourself. It's quite easy. Actually, I find this really interesting, so if you like I could write it for you.


Yeah, go ahead if you don't mind. I find C very challenging, sometimes even really hard because Java provides so much more support in my opinion. I try to learn it anyway.

Yeah, Java has significantly richer standart library, where is in C you have to write lots of stuff pretty much from zero. But once you have enough knowledge and experience with C, then it won't be more challenging than Java, and yet your apps will have much better performance.

On February 19 2013 09:23 Abductedonut wrote:
Show nested quote +
On February 19 2013 08:37 darkness wrote:
On February 19 2013 08:36 Abductedonut wrote:
On February 19 2013 08:28 darkness wrote:
I just want to express my appreciation of how much easier Java is than C. I also think I'm going to ask for help in the near future, haha. At least now I know why my C lecturer asks us to implement only math stuff. His major was math before switching to Computer Science. -.-

Edit: Ok, here's a simple problem.

Input two positive integers a and b (separated by one space). a and b can be very large (up to 99 digits). Output a+b. You are not allowed to use floating-point data types, including float, double, and long double.


Could you give a hint what to use or what to look for? Except for GMP (which may not be accepted by the Online Judge) and floating-point data types.


Keep in mind that your computer can only store 64-bit or 32-bit numbers. Your best bit is to store the numbers in an array and write the addition operation yourself. It's quite easy. Actually, I find this really interesting, so if you like I could write it for you.


Yeah, go ahead if you don't mind. I find C very challenging, sometimes even really hard because Java provides so much more support in my opinion. I try to learn it anyway.


This is by no means a pretty solution (I didn't include comments in the for loop that does the actual adding on purpose, variables are named stupidly, etc etc). Also, by no means is the code robust or error free. I didn't really test all the cases. I just wrote the program and verified that it kinda worked. It's up to you from here. Here you go.

Also, this code might go a little above your head. Sorry if it does!

+ Show Spoiler +

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[]
{
char a[100], b[100], temp[100], sum[101];
memset(sum,0,101);
scanf("%s",a);
scanf("%s",b);

//Swap the strings
if ( strlen(b) > strlen(a) )
{
strcpy(temp,b);
strcpy(b,a);
strcpy(a,temp);
}

// We could reuse temp but that's bad practice
char temp2[100];
strcpy(temp2,b);
//Fill b with zeros until strings are aligned
if( strlen(a) != strlen(b) )
{
int difference = strlen(a) - strlen(b);
memset(b,'0',difference);
strcpy(b+difference,temp2);
}

printf("A is: %s \n",a);
printf("B is: %s \n \n",b);
char carry = '0';
short int a_int = 0, b_int = 0, carry_int = 0;
char temp3[3];
temp3[0] = '\0';
temp3[1] = '\0';
temp3[2] = '\0';


for ( int i = 0; i < strlen(b); i++ )
{
a_int = a[strlen(a)-i-1] - '0'; //A small hack to convert a character to an int
b_int = b[strlen(b)-i-1] - '0';
carry_int = carry - '0';

sprintf(temp3,"%s%d",temp3,(a_int+b_int+carry_int));
sum[ strlen(a)-i-1 ] = (temp3[1] == NULL) ? temp3[0] : temp3[1];
carry = (temp3[1] != NULL) ? temp3[0] : '0';

temp3[0] = '\0';
temp3[1] = '\0';
}

printf("Sum is: %s \n",sum);
system("PAUSE");
return 0;
}

In his exercise numbers are supposed to be separated with space and if you try to sum 9 and 9 you'll end up with 8 instead of 18 ;P

Here's what I ended up with:
+ Show Spoiler +

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int sumNumberStrings(char *aStr, int aLen, char *bStr, int bLen, char *output);
void reverse(char *str);

int main(int argc, char *argv[])
{
char input[200];
char output[201];
char *delim;
int r;

gets(input);

delim = strchr(input, ' ');
if (delim == 0)
{
printf("bad string!\n");
return 1;
}

r = sumNumberStrings(input, delim - input, // number 1
delim + 1, strlen(delim + 1), // number 2
output);

if (r != 0) // sumNumberString failed - quit
{
printf("bad string!\n");
return 1;
}

printf("result: %s\n", output);
return 0;
}

int sumNumberStrings(char *a, int aLen, char *b, int bLen, char *output)
{
char *aEnd, *bEnd, *r;
int sum, carry, i;

sum = carry = i = 0;
aEnd = a + aLen - 1;
bEnd = b + bLen - 1;

while(aEnd >= a || bEnd >= b || sum != 0)
{
int aVal, bVal;

if ((aEnd >= a && !isdigit(*aEnd)) || (bEnd >= b && !isdigit(*bEnd))) return -1;

aVal = *aEnd - '0';
bVal = *bEnd - '0';

if (aEnd >= a) aEnd--;
else aVal = 0;
if (bEnd >= b) bEnd--;
else bVal = 0;

sum = aVal + bVal;

output[i++] = (sum + carry) % 10 + '0';
carry = (sum + carry) / 10;
}

if (output[i-1] == '0') i--;
output[i] = '\0';

// reverse output string
i--;

for (r = output; r < output + i; r++, i--)
{
char tmp = output[i];
output[i] = *r;
*r = tmp;
}

return 0;
}


I'm only studying C as well, so please do critique. By the way, darkness, should this program be able to sum floating point numbers? Anyway, adding such functionality would a be great exercise for you!
phar
Profile Joined August 2011
United States1080 Posts
Last Edited: 2013-02-19 02:29:42
February 19 2013 02:24 GMT
#5003
On February 19 2013 11:15 tuho12345 wrote:

Hi everyone, I'm a newbie in programming and Java specifically. I had a little experience with VB, which is significantly easier than Java or C I guess. So I'm kinda stuck right here and wish I'd have more time but it's due tomorrow and I'm struggling with other exams as well.

Here below is my code, and my question is how can I calculate the SalesTotal and SalesCount. I understand the logic but I have no idea how Java works.
Thanks

+ Show Spoiler +
/**
Assignment 2, CS49J, Spring 2013
Part B student
A cash register totals up sales and computes change due.
*/
public class CashRegister
{
private double purchase;
private double payment;

//... Add your code here
private double SalesTotal;
private int SalesCount;
/**
Constructs a cash register with no money in it.
*/
public CashRegister()
{
purchase = 0;
payment = 0;
//...Add your code here
SalesCount = 0;
SalesTotal = 0;
}

/**
Records the sale of an item.
@param amount the price of the item
*/
public void recordPurchase(double amount)
{
double total = purchase + amount;
//... Add your code here
//SalesTotal += total;
purchase = total;
}

/**
Enters the payment received from the customer.
@param amount the amount of the payment
*/
public void enterPayment(double amount)
{
payment = amount;
}

/**
Computes the change due and resets the machine for the next customer.
@return the change due to the customer
*/
public double giveChange()
{
double change = payment - purchase;
purchase = 0;
payment = 0;
return change;
}

/**
Get the total amount of all sales for the day.
@param return sale total
*/
//... Add your code here
public double getSalesTotal()
{

SalesTotal = SalesTotal + purchase;
return SalesTotal;

}



/**
Get the total number of sales for the day.
@param return the number of sales.
*/
//... Add your code here
public double getSalesCount()
{

return SalesCount;
}
/**
Reset counters and totals for the next days sales.
@param none
*/
//... Add your code here
public void reset()
{
SalesCount = 0;
payment = 0;
purchase = 0;
SalesTotal = 0;
}
}

In the future when posting code, please use proper indentation so that we can read it more easily.

Bad:
int foo() {
int bar;
return bar + 1;
}


Good:
int foo() {
int bar;
return bar + 1;
}



Also I'm not clear on exactly what you're asking. What are you trying to do? What part are you confused on? Do you know how a variable inside a class works?
Who after all is today speaking about the destruction of the Armenians?
tuho12345
Profile Blog Joined July 2011
4482 Posts
February 19 2013 02:48 GMT
#5004
On February 19 2013 11:24 phar wrote:
Show nested quote +
On February 19 2013 11:15 tuho12345 wrote:

Hi everyone, I'm a newbie in programming and Java specifically. I had a little experience with VB, which is significantly easier than Java or C I guess. So I'm kinda stuck right here and wish I'd have more time but it's due tomorrow and I'm struggling with other exams as well.

Here below is my code, and my question is how can I calculate the SalesTotal and SalesCount. I understand the logic but I have no idea how Java works.
Thanks

+ Show Spoiler +
/**
Assignment 2, CS49J, Spring 2013
Part B student
A cash register totals up sales and computes change due.
*/
public class CashRegister
{
private double purchase;
private double payment;

//... Add your code here
private double SalesTotal;
private int SalesCount;
/**
Constructs a cash register with no money in it.
*/
public CashRegister()
{
purchase = 0;
payment = 0;
//...Add your code here
SalesCount = 0;
SalesTotal = 0;
}

/**
Records the sale of an item.
@param amount the price of the item
*/
public void recordPurchase(double amount)
{
double total = purchase + amount;
//... Add your code here
//SalesTotal += total;
purchase = total;
}

/**
Enters the payment received from the customer.
@param amount the amount of the payment
*/
public void enterPayment(double amount)
{
payment = amount;
}

/**
Computes the change due and resets the machine for the next customer.
@return the change due to the customer
*/
public double giveChange()
{
double change = payment - purchase;
purchase = 0;
payment = 0;
return change;
}

/**
Get the total amount of all sales for the day.
@param return sale total
*/
//... Add your code here
public double getSalesTotal()
{

SalesTotal = SalesTotal + purchase;
return SalesTotal;

}



/**
Get the total number of sales for the day.
@param return the number of sales.
*/
//... Add your code here
public double getSalesCount()
{

return SalesCount;
}
/**
Reset counters and totals for the next days sales.
@param none
*/
//... Add your code here
public void reset()
{
SalesCount = 0;
payment = 0;
purchase = 0;
SalesTotal = 0;
}
}

In the future when posting code, please use proper indentation so that we can read it more easily.

Bad:
int foo() {
int bar;
return bar + 1;
}


Good:
int foo() {
int bar;
return bar + 1;
}



Also I'm not clear on exactly what you're asking. What are you trying to do? What part are you confused on? Do you know how a variable inside a class works?

Sorry, I just edited. My question is I'm trying to total the amount of money at the end of the day. It called SalesTotal or getSalesTotal method, I don't know how to add up the total amount of money after all that transaction. I can't use the tester tool to print it out.

public double getSalesTotal()
{

      SalesTotal += purchase ;
      return SalesTotal;

}
phar
Profile Joined August 2011
United States1080 Posts
February 19 2013 03:55 GMT
#5005
On February 19 2013 11:48 tuho12345 wrote:
Show nested quote +
On February 19 2013 11:24 phar wrote:
On February 19 2013 11:15 tuho12345 wrote:

Hi everyone, I'm a newbie in programming and Java specifically. I had a little experience with VB, which is significantly easier than Java or C I guess. So I'm kinda stuck right here and wish I'd have more time but it's due tomorrow and I'm struggling with other exams as well.

Here below is my code, and my question is how can I calculate the SalesTotal and SalesCount. I understand the logic but I have no idea how Java works.
Thanks

+ Show Spoiler +
/**
Assignment 2, CS49J, Spring 2013
Part B student
A cash register totals up sales and computes change due.
*/
public class CashRegister
{
private double purchase;
private double payment;

//... Add your code here
private double SalesTotal;
private int SalesCount;
/**
Constructs a cash register with no money in it.
*/
public CashRegister()
{
purchase = 0;
payment = 0;
//...Add your code here
SalesCount = 0;
SalesTotal = 0;
}

/**
Records the sale of an item.
@param amount the price of the item
*/
public void recordPurchase(double amount)
{
double total = purchase + amount;
//... Add your code here
//SalesTotal += total;
purchase = total;
}

/**
Enters the payment received from the customer.
@param amount the amount of the payment
*/
public void enterPayment(double amount)
{
payment = amount;
}

/**
Computes the change due and resets the machine for the next customer.
@return the change due to the customer
*/
public double giveChange()
{
double change = payment - purchase;
purchase = 0;
payment = 0;
return change;
}

/**
Get the total amount of all sales for the day.
@param return sale total
*/
//... Add your code here
public double getSalesTotal()
{

SalesTotal = SalesTotal + purchase;
return SalesTotal;

}



/**
Get the total number of sales for the day.
@param return the number of sales.
*/
//... Add your code here
public double getSalesCount()
{

return SalesCount;
}
/**
Reset counters and totals for the next days sales.
@param none
*/
//... Add your code here
public void reset()
{
SalesCount = 0;
payment = 0;
purchase = 0;
SalesTotal = 0;
}
}

In the future when posting code, please use proper indentation so that we can read it more easily.

Bad:
int foo() {
int bar;
return bar + 1;
}


Good:
int foo() {
int bar;
return bar + 1;
}



Also I'm not clear on exactly what you're asking. What are you trying to do? What part are you confused on? Do you know how a variable inside a class works?

Sorry, I just edited. My question is I'm trying to total the amount of money at the end of the day. It called SalesTotal or getSalesTotal method, I don't know how to add up the total amount of money after all that transaction. I can't use the tester tool to print it out.

Show nested quote +
public double getSalesTotal()
{

      SalesTotal += purchase ;
      return SalesTotal;

}

Do you know how variables inside a class work?

public class Foo {
private int fooVal;

public void setFoo(int val) {
this.fooVal = val;
}

public int getFoo() {
return foo;
}

public static blahblah main(more blah) {
Foo foo = new Foo();
foo.setFoo(5);
System.out.println("Number is: " + foo.getFoo()); // Prints 5;
foo.setFoo(7);
System.out.println("Number is: " + foo.getFoo()); // Prints 7;
}
Who after all is today speaking about the destruction of the Armenians?
tuho12345
Profile Blog Joined July 2011
4482 Posts
February 19 2013 05:45 GMT
#5006
On February 19 2013 12:55 phar wrote:
Show nested quote +
On February 19 2013 11:48 tuho12345 wrote:
On February 19 2013 11:24 phar wrote:
On February 19 2013 11:15 tuho12345 wrote:

Hi everyone, I'm a newbie in programming and Java specifically. I had a little experience with VB, which is significantly easier than Java or C I guess. So I'm kinda stuck right here and wish I'd have more time but it's due tomorrow and I'm struggling with other exams as well.

Here below is my code, and my question is how can I calculate the SalesTotal and SalesCount. I understand the logic but I have no idea how Java works.
Thanks

+ Show Spoiler +
/**
Assignment 2, CS49J, Spring 2013
Part B student
A cash register totals up sales and computes change due.
*/
public class CashRegister
{
private double purchase;
private double payment;

//... Add your code here
private double SalesTotal;
private int SalesCount;
/**
Constructs a cash register with no money in it.
*/
public CashRegister()
{
purchase = 0;
payment = 0;
//...Add your code here
SalesCount = 0;
SalesTotal = 0;
}

/**
Records the sale of an item.
@param amount the price of the item
*/
public void recordPurchase(double amount)
{
double total = purchase + amount;
//... Add your code here
//SalesTotal += total;
purchase = total;
}

/**
Enters the payment received from the customer.
@param amount the amount of the payment
*/
public void enterPayment(double amount)
{
payment = amount;
}

/**
Computes the change due and resets the machine for the next customer.
@return the change due to the customer
*/
public double giveChange()
{
double change = payment - purchase;
purchase = 0;
payment = 0;
return change;
}

/**
Get the total amount of all sales for the day.
@param return sale total
*/
//... Add your code here
public double getSalesTotal()
{

SalesTotal = SalesTotal + purchase;
return SalesTotal;

}



/**
Get the total number of sales for the day.
@param return the number of sales.
*/
//... Add your code here
public double getSalesCount()
{

return SalesCount;
}
/**
Reset counters and totals for the next days sales.
@param none
*/
//... Add your code here
public void reset()
{
SalesCount = 0;
payment = 0;
purchase = 0;
SalesTotal = 0;
}
}

In the future when posting code, please use proper indentation so that we can read it more easily.

Bad:
int foo() {
int bar;
return bar + 1;
}


Good:
int foo() {
int bar;
return bar + 1;
}



Also I'm not clear on exactly what you're asking. What are you trying to do? What part are you confused on? Do you know how a variable inside a class works?

Sorry, I just edited. My question is I'm trying to total the amount of money at the end of the day. It called SalesTotal or getSalesTotal method, I don't know how to add up the total amount of money after all that transaction. I can't use the tester tool to print it out.

public double getSalesTotal()
{

      SalesTotal += purchase ;
      return SalesTotal;

}

Do you know how variables inside a class work?

public class Foo {
private int fooVal;

public void setFoo(int val) {
this.fooVal = val;
}

public int getFoo() {
return foo;
}

public static blahblah main(more blah) {
Foo foo = new Foo();
foo.setFoo(5);
System.out.println("Number is: " + foo.getFoo()); // Prints 5;
foo.setFoo(7);
System.out.println("Number is: " + foo.getFoo()); // Prints 7;
}

yes, i see the difference between Static and non static.
phar
Profile Joined August 2011
United States1080 Posts
Last Edited: 2013-02-19 05:53:56
February 19 2013 05:52 GMT
#5007
Sort of... static method and static variable mean slightly different things though:


public class Foo {
private static int fooVal; // shared between all instances of Foo

public void setFoo(int val) {
this.fooVal = val;
}

public int getFoo() {
return foo;
}

public static blahblah main(more blah) {
Foo foo = new Foo();
Foo other = new Foo();
foo.setFoo(5);
System.out.println("Number is: " + foo.getFoo()); // Prints 5;
System.out.println("Number is: " + other.getFoo()); // Prints 5;
other.setFoo(7);
System.out.println("Number is: " + foo.getFoo()); // Prints 7;
System.out.println("Number is: " + other.getFoo()); // Prints 7;
}


You shouldn't need a static variable if you only have one instance of whatever class it is you're using.
Who after all is today speaking about the destruction of the Armenians?
Wry
Profile Joined October 2011
Canada25 Posts
Last Edited: 2013-02-19 06:10:28
February 19 2013 06:04 GMT
#5008
On February 19 2013 11:15 tuho12345 wrote:
Hi everyone, I'm a newbie in programming and Java specifically. I had a little experience with VB, which is significantly easier than Java or C I guess. So I'm kinda stuck right here and wish I'd have more time but it's due tomorrow and I'm struggling with other exams as well.

Here below is my code, and my question is how can I calculate the SalesTotal and SalesCount. I understand the logic but I have no idea how Java works.
Thanks

+ Show Spoiler +



/**
Assignment 2, CS49J, Spring 2013
Part B student
A cash register totals up sales and computes change due.
*/
public class CashRegister
{
      private double purchase;
      private double payment;

//... Add your code here
      private double SalesTotal;
      private int SalesCount;
/**
Constructs a cash register with no money in it.
*/
public CashRegister()
{
       purchase = 0;
       payment = 0;
      SalesCount = 0;
       SalesTotal = 0;
}

/**
Records the sale of an item.
@param amount the price of the item
*/
public void recordPurchase(double amount)
{
      double total = purchase + amount;
//... Add your code here
       purchase = total;

}

/**
Enters the payment received from the customer.
@param amount the amount of the payment
*/
public void enterPayment(double amount)
{
      payment = amount;
      SalesCount++;
}

/**
Computes the change due and resets the machine for the next customer.
@return the change due to the customer
*/
public double giveChange()
{
      double change = payment - purchase;
      purchase = 0;
       payment = 0;
      return change;
}

/**
Get the total amount of all sales for the day.
@param return sale total
*/
//... Add your code here
public double getSalesTotal()
{

      SalesTotal = purchase + purchase;
      return SalesTotal;

}



/**
Get the total number of sales for the day.
@param return the number of sales.
*/
//... Add your code here

public double getSalesCount()
{
      return SalesCount;
}
/**
Reset counters and totals for the next days sales.
@param none
*/
//... Add your code here
public void reset()
{
      SalesCount = 0;
      payment = 0;
      purchase = 0;
      SalesTotal = 0;
}
}



Not completely sure what SalesTotal is, but I am assuming it means the total amount of all the purchases? (eg. 3 customers buy items worth $3.00, $2.50 and $1.75, SalesTotal = 6.25 and SalesCount = 3).

First, when creating 'getter' methods, such as getSalesTotal(), you should only really be returning the value you desire and not calculating it in that method. A more logical way to do it would be to add the purchase amount to the sales total as you receive payment or record purchases.

Also, you may want to think of some error cases because it seems that a customer can input amounts less than the item cost and your register will accept that.

Ex. Item worth $100:
recordPurchase(100)
enterPayment(50)
giveChange();

= You lose $50.

Edit: unless the main handles that, though you might want to specify that in comments. (now that I look at it again, it's not completely nonsensical with a main function that handles the register).
tuho12345
Profile Blog Joined July 2011
4482 Posts
February 19 2013 06:22 GMT
#5009
On February 19 2013 15:04 Wry wrote:
Show nested quote +
On February 19 2013 11:15 tuho12345 wrote:
Hi everyone, I'm a newbie in programming and Java specifically. I had a little experience with VB, which is significantly easier than Java or C I guess. So I'm kinda stuck right here and wish I'd have more time but it's due tomorrow and I'm struggling with other exams as well.

Here below is my code, and my question is how can I calculate the SalesTotal and SalesCount. I understand the logic but I have no idea how Java works.
Thanks

+ Show Spoiler +



/**
Assignment 2, CS49J, Spring 2013
Part B student
A cash register totals up sales and computes change due.
*/
public class CashRegister
{
      private double purchase;
      private double payment;

//... Add your code here
      private double SalesTotal;
      private int SalesCount;
/**
Constructs a cash register with no money in it.
*/
public CashRegister()
{
       purchase = 0;
       payment = 0;
      SalesCount = 0;
       SalesTotal = 0;
}

/**
Records the sale of an item.
@param amount the price of the item
*/
public void recordPurchase(double amount)
{
      double total = purchase + amount;
//... Add your code here
       purchase = total;

}

/**
Enters the payment received from the customer.
@param amount the amount of the payment
*/
public void enterPayment(double amount)
{
      payment = amount;
      SalesCount++;
}

/**
Computes the change due and resets the machine for the next customer.
@return the change due to the customer
*/
public double giveChange()
{
      double change = payment - purchase;
      purchase = 0;
       payment = 0;
      return change;
}

/**
Get the total amount of all sales for the day.
@param return sale total
*/
//... Add your code here
public double getSalesTotal()
{

      SalesTotal = purchase + purchase;
      return SalesTotal;

}



/**
Get the total number of sales for the day.
@param return the number of sales.
*/
//... Add your code here

public double getSalesCount()
{
      return SalesCount;
}
/**
Reset counters and totals for the next days sales.
@param none
*/
//... Add your code here
public void reset()
{
      SalesCount = 0;
      payment = 0;
      purchase = 0;
      SalesTotal = 0;
}
}



Not completely sure what SalesTotal is, but I am assuming it means the total amount of all the purchases? (eg. 3 customers buy items worth $3.00, $2.50 and $1.75, SalesTotal = 6.25 and SalesCount = 3).

First, when creating 'getter' methods, such as getSalesTotal(), you should only really be returning the value you desire and not calculating it in that method. A more logical way to do it would be to add the purchase amount to the sales total as you receive payment or record purchases.

Also, you may want to think of some error cases because it seems that a customer can input amounts less than the item cost and your register will accept that.

Ex. Item worth $100:
recordPurchase(100)
enterPayment(50)
giveChange();

= You lose $50.

Edit: unless the main handles that, though you might want to specify that in comments. (now that I look at it again, it's not completely nonsensical with a main function that handles the register).

Thank you Wry, it's so simple haha. I made that change to the SalesCount but not the SalesTotal, so silly.
Oaky
Profile Joined August 2012
United States95 Posts
February 19 2013 06:57 GMT
#5010
Im curious how long, and how much effort, would it take to get relatively competent at javascript/php or some other web dev. language so i could offer to redo parts of my schools hideous website. I am intermediate with python.
SOOOOOOO MANY BANELINGS!
obesechicken13
Profile Blog Joined July 2008
United States10467 Posts
Last Edited: 2013-02-19 07:16:09
February 19 2013 07:15 GMT
#5011
On February 19 2013 15:57 Oaky wrote:
Im curious how long, and how much effort, would it take to get relatively competent at javascript/php or some other web dev. language so i could offer to redo parts of my schools hideous website. I am intermediate with python.

Making sites look good is more about graphic design than html or css imo.

What prior experience do you have?
I think in our modern age technology has evolved to become more addictive. The things that don't give us pleasure aren't used as much. Work was never meant to be fun, but doing it makes us happier in the long run.
Oaky
Profile Joined August 2012
United States95 Posts
February 19 2013 07:21 GMT
#5012
On February 19 2013 16:15 obesechicken13 wrote:
Show nested quote +
On February 19 2013 15:57 Oaky wrote:
Im curious how long, and how much effort, would it take to get relatively competent at javascript/php or some other web dev. language so i could offer to redo parts of my schools hideous website. I am intermediate with python.

Making sites look good is more about graphic design than html or css imo.

What prior experience do you have?

Pretty minimal, been teaching myself python for a few weeks.
SOOOOOOO MANY BANELINGS!
AmericanUmlaut
Profile Blog Joined November 2010
Germany2581 Posts
February 19 2013 08:34 GMT
#5013
On February 19 2013 15:57 Oaky wrote:
Im curious how long, and how much effort, would it take to get relatively competent at javascript/php or some other web dev. language so i could offer to redo parts of my schools hideous website. I am intermediate with python.

That kind of depends on what you mean by "relatively competent." If you just want to make a nice-looking website, you really don't need to go crazy with Javascript and PHP - your PHP just needs to generate decent HTML, you'll want to use CSS to make your layout look nice, and Javascript is probably only necessary if you want to animate something, which is pretty easy if you just use jQuery (which has become pretty much the standard Javascript library, so it's very useful to be familiar with).

Without looking at your webpage, I can only go on what I've seen in other beginners, but I would guess that you're having two problems: Your HTML is likely not well organized, and you either don't have a good sense of what makes a page look nice or you don't have a strong enough grasp of CSS to get the effect that you want. Without seeing code it's hard to help with those things, but if you want to post a link to what you're working on, or a chunk of code that's giving you trouble, then I'd be happy to take a look.
The frumious Bandersnatch
Shield
Profile Blog Joined August 2009
Bulgaria4824 Posts
Last Edited: 2013-02-20 15:16:06
February 19 2013 22:01 GMT
#5014
Hey guys, I need a bit of help for C.

What I expect to do:

I'm trying to implement ROT13: http://en.wikipedia.org/wiki/ROT13
Every char (int in this case) is either incremented 13 digits or decremented based on conditions. Then, I'm trying to copy each character to 'string' which I output in the end.

What happens:
I get a 'Segmentation fault' and also these warnings:
test.c: In function Б─≤rot13Б─≥:
test.c:12: warning: passing argument 2 of Б─≤strcatБ─≥ makes pointer from integer without a cast
/usr/include/string.h:136: note: expected Б─≤const char * __restrict__Б─≥ but argument is of type Б─≤charБ─≥
test.c:16: warning: passing argument 2 of Б─≤strcatБ─≥ makes pointer from integer without a cast
/usr/include/string.h:136: note: expected Б─≤const char * __restrict__Б─≥ but argument is of type Б─≤charБ─≥
test.c:19: warning: passing argument 2 of Б─≤strcatБ─≥ makes pointer from integer without a cast
/usr/include/string.h:136: note: expected Б─≤const char * __restrict__Б─≥ but argument is of type Б─≤charБ─≥




tofucake
Profile Blog Joined October 2009
Hyrule19174 Posts
February 19 2013 22:03 GMT
#5015
you declare int c

then compare int c to several const chars (for one)

Another: you need to cast to a pointer to a character, not to a character.
Liquipediaasante sana squash banana
Shield
Profile Blog Joined August 2009
Bulgaria4824 Posts
February 19 2013 22:11 GMT
#5016
On February 20 2013 07:03 tofucake wrote:
you declare int c

then compare int c to several const chars (for one)

Another: you need to cast to a pointer to a character, not to a character.


Do you mean this comparison: (c >= 'A' && c <= 'M') || (c >= 'a' && c <= 'M')? If yes, I think it's perfectly fine with gcc.
I'm not sure how to do the 2nd thing you mentioned though. Pointers are still new to me.
InRaged
Profile Joined February 2007
1047 Posts
February 19 2013 22:19 GMT
#5017
Casting to pointer won't solve problem.

strcat.
strcat expects zero-terminated string for both of its arguments.
You give it int, it tries to follow the adress inside int, which is obviously invalid, and so you get segfault.

You need some temp string:
char *tmp = "a";
Then you put your adjusted char there
tmp[0] = c;
and then pass it to strcat
strcat(string, tmp);
Shield
Profile Blog Joined August 2009
Bulgaria4824 Posts
Last Edited: 2013-02-20 15:16:37
February 19 2013 22:28 GMT
#5018
On February 20 2013 07:19 InRaged wrote:
Casting to pointer won't solve problem.

strcat.
strcat expects zero-terminated string for both of its arguments.
You give it int, it tries to follow the adress inside int, which is obviously invalid, and so you get segfault.

You need some temp string:
char *tmp = "a";
Then you put your adjusted char there
tmp[0] = c;
and then pass it to strcat
strcat(string, tmp);


It doesn't give warnings now, but it still says:
-bash-4.1$ ./a.out
abcd
Segmentation fault

delHospital
Profile Blog Joined December 2010
Poland261 Posts
February 19 2013 22:43 GMT
#5019
On February 20 2013 07:19 InRaged wrote:
Casting to pointer won't solve problem.

strcat.
strcat expects zero-terminated string for both of its arguments.
You give it int, it tries to follow the adress inside int, which is obviously invalid, and so you get segfault.

You need some temp string:
char *tmp = "a";
Then you put your adjusted char there
tmp[0] = c;
and then pass it to strcat
strcat(string, tmp);

I'd recommend
char tmp[] = "a";
instead of
char *tmp = "a";

The first one allocates a 2 character array, which is just what we need, while the second one allocates a pointer to a string constant, which could be stored in read-only memory.

Other than that, this should work, but also keep in mind that your "char string[SIZE]" array may contain garbage at the start, which would cause problems with strcat. The easiest way to clear it is (google to see what it does):
memset(string, 0, SIZE);

Also, your program will explode if it receives more than 99 characters.
InRaged
Profile Joined February 2007
1047 Posts
Last Edited: 2013-02-19 23:16:35
February 19 2013 22:58 GMT
#5020
Thank you, delHospital. Should be char tmp[];

darkness, If you can use strncat instead of strcat then instead of tmp variable you could do
strncat(string, (char *)&c, 1);
The casting is required in such case, cause your c is int and not char (but it isn't as portable, see Mstring's responce). Last argument tells strncat how much bytes to copy.

Also there is a bug in your algorithm. Check your if conditions to find it ;P
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