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 03162011, 03:44 PM #1Member
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summation in java using for loops
I am trying to make a summation calculator for the following equation:
Where i is the lower limit (in this case it will always be 0) and n is the upper limit (in this problem the user will be asked to enter an integer value of the upper limit).
Here is my code (so far):
import java.io.*;
public class summation
{
public static void main(String args[]) throws IOException
{
BufferedReader keybd = new BufferedReader(new InputStreamReader(System.in));
int ul;
System.out.print("Enter the upper limit: ");
ul = Integer.parseInt(keybd.readLine());
}
}
I don't understand how to use a for loop to calculate the sum.
After that I got stuck. I appreciate any help i can get thanks! :)Last edited by java157; 03162011 at 03:48 PM.
 03162011, 03:52 PM #2
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You will need some math functions.
Math.pow returns the value of the first argument raised to the power of the second argument.
Java Code:double Math.pow(double a, double b)
To calculate the factorial make your own loop e.g.
Java Code:private int factorial(int number) { int counter = number; int answer = counter; while (counter > 1) { answer *= counter; } return answer; }
And then make a forloop over your entire equation with your limits put in e.g.
Java Code:double totalSum = 0; double sum = 0; for (i=0; i<=n; i++) { ... totalSum += sum; } return totalSum;
But beware whereever you add an integer to the sum, convert it to a double first, or cast it to a double.Last edited by ozzyman; 03162011 at 04:57 PM.
 03172011, 08:33 AM #4Member
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