While loop numbers sum

Question

I need help on how to calculate sum of the numbers that while loop prints. I have to get numbers 1 to 100 using while loop and calculate all those together. Like 1+2+3...+98+99+100. I can get numbers but can't calculate them together. Here's my code:

public class Loops {
    public static void main(String[] args) throws Exception {
        int i = 1;
        while (i < 101) {
           System.out.print(i);
           i = i + 1;
        }
    }
}

How do I make it only print the last sum? If I try to trick the equation it just hangs.

Are you asking how to declare another variable and add values of i to it? — Ondrej Tucny
– Ondrej Tucny, Commented Nov 18, 2013 at 9:07

Tushar Thakur · Accepted Answer · 2013-11-18 09:15:13Z

3

First either change your sum variable or index variable

public class Loops {
 public static void main(String[] args) {
  int sum = 0;
  int i = 1;
  while (i < 101) {
   sum = sum + i;
   ++i;
  }
  System.out.println(sum);
}

answered Nov 18, 2013 at 9:15

Tushar Thakur

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1 Comment

user4294909 Over a year ago

Nice calculate index++ and then just add sum and print it

Maroun · Accepted Answer · 2013-11-18 08:57:35Z

2

Use another variable instead of i which is the loop variable:

int i   = 1;
int sum = 0;
while (i < 101) {
  sum += i;
  i++;
}

Now sum will contain the desired output. In the previous version, you didn't really loop on all values of i from 1 to 101.

answered Nov 18, 2013 at 8:57

Maroun

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Comments

Ondrej Tucny · Accepted Answer · 2013-11-18 09:08:50Z

1

Your sum (i) is also your index. So each time you add to it, you're skipping numbers which you want to add to it.

public class Loops {
 public static void main(String[] args) {
  int sum = 0;
  int i = 1;
  while (i < 101) {
   //System.out.print(i);
   sum = sum + i;
   ++i;
  }
  System.out.println(sum);
}

Alternatively, use the Gauss sum: n(n+1)/2

So, the end sum is 100(101)/2 = 5050

edited Nov 18, 2013 at 9:08

Ondrej Tucny

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answered Nov 18, 2013 at 9:03

vangelion

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Comments

peter.petrov · Accepted Answer · 2014-11-28 00:20:52Z

1

Try the following. Moved the values around a bit to ensure that you add up to 100 and always show the sum.

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

    int i = 1;
    long tot = 1;

    while (i < 100) {   
       i += 1;
       tot += i;
       System.out.print("Number :" + i + "  ,sum="+tot);
    }

}

edited Nov 28, 2014 at 0:20

peter.petrov

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answered Nov 18, 2013 at 9:01

Jean B

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Comments

phdhiren · Accepted Answer · 2013-11-18 09:03:59Z

-3

public class Loops {
  public static void main(String[] args) throws Exception {
    int i = 1;
    int sum = 0;
    while (i < 101) {
       sum = i + 1;
    }
    System.out.print(sum);
  }
}

answered Nov 18, 2013 at 9:03

phdhiren

1

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