# Thread: Help finding sum of an array

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## Help finding sum of an array

I have to make a program where I have the user enter the amount of numbers they want to input, and then have a menu that allows them to see the sum, average, printed order, reverse order, number of even numbers, and number of odd numbers. To find the sum of the numbers, I have to know how many numbers the user has entered, but I'm not sure how. (It's choice 1 in the program)

Java Code:
```import cs1.Keyboard;
import java.util.*;
public class moreArray
{
public static void main(String[] args)
{

System.out.println("How many elements would you like to enter");
int[] a = new int[numElements];
int count;
int[]b=new int[numElements];

if(numElements<=0)
System.out.println("Invalid number. Must be greater than 0");

else
{

for (count=0; count<numElements; count++)
{
System.out.println("Please enter a number for bucket " +(count+1));
}

System.out.println("1. Sum of numbers");
System.out.println("2. Average of numbers");
System.out.println("3. Print list backwards");
System.out.println("4. Print list forwards");
System.out.println("5. Count even numbers");
System.out.println("6. Count odd numbers");
System.out.println("7. Quit");

if(choice==1)
{

}

if(choice==2)
{

}```

Edit: Program isn't done. I'm just having trouble with the first choice
Last edited by HalfAZN; 04-19-2012 at 05:24 PM.  Reply With Quote

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## Re: Help finding sum of an array

Sounds like you are putting these numbers into an array. Why not use the length of the array to determine how many numbers the user entered?  Reply With Quote

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## Re: Help finding sum of an array Originally Posted by Wnt2bsleepin Why not use the length of the array to determine how many numbers the user entered?
How do I do this?  Reply With Quote

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## Re: Help finding sum of an array Originally Posted by HalfAZN How do I do this?
You can get the length of the array like this:

Java Code:
`arrayname.length;`
Notice there is no () there.  Reply With Quote

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## Re: Help finding sum of an array Originally Posted by Wnt2bsleepin You can get the length of the array like this:

Java Code:
`arrayname.length;`
Notice there is no () there.
I sent an int (k) equal to a.length, and everything compiled, but when I ran it

Java Code:
```if(choice==1)
{

System.out.println("Sum: " +a[k]);
}```   Reply With Quote

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## Re: Help finding sum of an array

Can you post the rest of the code with the correction you added? You seem to be trying to print out an array that doesn't exits. If you wanted to print out the last element in the array, use k-1.  Reply With Quote

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## Re: Help finding sum of an array

Java Code:
```import cs1.Keyboard;
import java.util.*;
public class moreArray
{
public static void main(String[] args)
{

System.out.println("How many elements would you like to enter");
int[] a = new int[numElements];
int count;
int[]b=new int[numElements];
boolean go;
int k=a.length;

int counter;

if(numElements<=0)
System.out.println("Invalid number. Must be greater than 0");

else
{

for (count=0; count<numElements; count++)
{
System.out.println("Please enter a number for bucket " +(count+1));
}

System.out.println("1. Sum of numbers");
System.out.println("2. Average of numbers");
System.out.println("3. Print list forwards");
System.out.println("4. Print list backwards");
System.out.println("5. Count even numbers");
System.out.println("6. Count odd numbers");
System.out.println("7. Quit");

if(choice==1)
{

System.out.println("Sum: " +a[k]);
}

if(choice==2)
{

}

if(choice==3)
{

}

}

}

}```

I realize that a[k] isn't the sum, but not sure where to go
Last edited by HalfAZN; 04-20-2012 at 12:13 AM.  Reply With Quote

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## Re: Help finding sum of an array

If you want to sum up the elements in the array, you should use a loop.  Reply With Quote

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## Re: Help finding sum of an array

What would that look like? I'm assuming it would be a for loop, but I"m not sure how to construct it  Reply With Quote

10. AN21XX Join Date
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## Re: Help finding sum of an array

Try to use the for loop, you should come back with the new code if you have trouble - it will look similar to
Java Code:
`for(int i=0; i<myarray.length; i++) iResult += myarray[i];`
I would also suggest you read about using the switch() statement for your choice evaluation at the end of the program.
Last edited by Sierra; 04-20-2012 at 09:09 AM.  Reply With Quote

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## Re: Help finding sum of an array

Java Code:
```if(choice==1)
{

for( count=0; count<a.length; count++)
{
countResult += a[count];
}
System.out.println("Sum: " +a[k]);
}```
Is this what it should look like? It gets an error, so not sure  Reply With Quote

12. AN21XX Join Date
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## Re: Help finding sum of an array

It would be helpful if you tell us WHAT error... ;)
I would say the sum is countResult, not a[k], right?  Reply With Quote

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## Re: Help finding sum of an array Originally Posted by Sierra It would be helpful if you tell us WHAT error... ;)
I would say the sum is countResult, not a[k], right?
Java Code:
```if(choice==1)
{

for( count=0; count<a.length; count++)
{
countResult += a[count];
}
System.out.println("Sum: " +a[k]);
}```

Errors:

symbol : variable countResult
countResult += a[count];

symbol : variable countResult
System.out.println("Sum: " +countResult);  Reply With Quote

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## Re: Help finding sum of an array Originally Posted by HalfAZN Java Code:
```if(choice==1)
{

for( count=0; count<a.length; count++)
{
countResult += a[count];
}
System.out.println("Sum: " +a[k]);
}```

Errors:

symbol : variable countResult
countResult += a[count];

symbol : variable countResult
System.out.println("Sum: " +countResult);
Where did you define CountResult?  Reply With Quote

15. AN21XX Join Date
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## Re: Help finding sum of an array

Probably because you did not declare that variable... and if you are on it, remember to initialize it with zero before you enter the loop. :)  Reply With Quote

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## Re: Help finding sum of an array

Thanks to both of you. That turned out to be the problem. Didn't define CountResult ._.  Reply With Quote

arrays, java 