Adding prime number under a limit

Question

I want to add prime numbers under two million, and for some reason it keeps running with no output. After some testing I know that the error itself is in the the addprimes function however from what I understand the program should return an output.

static ArrayList<Integer> primes = new ArrayList<Integer>();

public static void findPrimes(int limit)
{
    primes.add(2);
    int Number = 3;
    int n = 0;
    boolean add = true;

    if(Number % 2 != 0)
        primes.add(Number);

    for(int i = Number; i<limit; i+=2)
    {
        n = 2;
        add = true;


        while(n < i)
        {
            if(i % n == 0)
            {
                add = false;
                continue;
            }
            n++;
        }


        if(add == true)
            primes.add(i);

    }
}


public static int addPrimes()
{
    int Total = 0;
    int temp = 0;
    for(int i = 0; i < primes.size(); i++)
    {
        temp = primes.get(i);
        Total += temp;
    }
    return Total;

}
}

score 0 · Accepted Answer · edited May 23 '17 at 12:33

0

You call continue without increment the value of n.

Try updating while loop to the following:

while(n < i)
{
   if(i % n == 0)
   {
       add = false;
       n++;
       continue;
   }
   else
       n++;
}

Check the answers of this question for more information about continue.

Update

In case your code ended up with too big numbers, then you have to use another data-types like Long, Double ..etc.

edited May 23 '17 at 12:33

Community

1
1

answered Feb 02 '17 at 02:20

Kh.Taheri

946
1
10
25

Thanks now it works for int, however if the number is too big then like the problem asks, then it does not but I think I know how to fix this issue. – Rpmp Feb 02 '17 at 02:32
Good luck, but if you found my answer helpful; you could check it as a Correct Answer ;) – Kh.Taheri Feb 02 '17 at 02:33

score 0 · Answer 2 · answered Feb 02 '17 at 02:39

0

You can just comment out continue to come out of infinite loop.
I can see that value 3 is repeating in the prime number list for that you can comment out these lines
```
//    if(Number % 2 != 0) 
//          primes.add(Number);
```

answered Feb 02 '17 at 02:39

Kiran Bhagwat

574
1
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13

Adding prime number under a limit

2 Answers2