How to solve error java.lang.ArithmeticException when finding prime numbers 1 to 100

Question

When the program is finding the prime numbers, it compiles.

But an error occurred during runtime. How can I fix it ?

What is the easiest way of finding prime numbers?

Error :

Exception in thread "main" java.lang.ArithmeticException: / by zero
    at PrimeNumbers.main(PrimeNumbers.java:6)

Code :

import java.util.*;

class PrimeNumbers { 

    public static void main(String args[]) {
        for (int i = 0; i <= 100; i++) {
            for (int j = 0; j < i; j++) {
                if (i % j == 0) {
                    break;
                } else {
                    System.out.println(i);
                }
            }
        }
    }
}

[ArithmeticException](https://stackoverflow.com/questions/2717032/arithmeticexception-java) — SatyaTNV, Dec 23 '17 at 09:50
No, `j` needs to start from 2 not from 1. If `j` starts from 1, you won't get the error, but you won't get any prime numbers shown. — Dawood ibn Kareem, Dec 23 '17 at 09:53
Possible duplicate of [Calculating and printing the nth prime number](https://stackoverflow.com/questions/9625663/calculating-and-printing-the-nth-prime-number) — SatyaTNV, Dec 23 '17 at 09:56

Oguz Ozcan · Answer 1 · 2017-12-23T10:01:45.490

1

You need to change your second for loop to start from 1 not 0. Because modular of zero is an error.

 for(int j=1;j<i;j++){
        if(i%j==0){

edited Dec 23 '17 at 10:01

answered Dec 23 '17 at 09:51

Oguz Ozcan

1,497
13
21

This isn't actually correct. See my comment under the question. – Dawood ibn Kareem Dec 23 '17 at 09:53
But the error you get is because of your loop starting from 0. – Oguz Ozcan Dec 23 '17 at 09:54
Yes, that's true, but OP needs to change it to start from 2, not to start from 1. – Dawood ibn Kareem Dec 23 '17 at 09:55
When it is 1,it runs.But no output.When it is 2,it runs and give the output.Thank you all. – K.Anuradha Dec 23 '17 at 13:38

score 1 · Accepted Answer · answered Dec 23 '17 at 09:58

1

You must change your code like this:

class PrimeNumbers{
public static void main(String args[])
{
    boolean flag;
    for(int i=1;i<=100;i++)
    {
        flag = true;
        for(int j=2;j<=(i/2);j++){
            if(i%j==0)
                flag = false;;
        if(flag == true)
           System.out.println(i);
    }
}

answered Dec 23 '17 at 09:58

Hossein

314
3
12

Thank Hossein. Yes it prints the prime numbers.But one number may print multiple times.Why is that? – K.Anuradha Dec 23 '17 at 13:36

score 0 · Answer 3 · answered Dec 23 '17 at 10:06

0

You have i = 0 and j = 0 in the first iteration of your loop. In order to obtain the modulus, i is divided by j. Therefore, you are performing in the first iteration:

0 / 0

Thus getting the divide by zero exception.

answered Dec 23 '17 at 10:06

ReverseEffect

133
6

Ok.Got it.Thank you. – K.Anuradha Dec 23 '17 at 13:40

Oleg Cherednik · Answer 4 · 2017-12-23T13:44:17.570

0

There are two possible ways of prime number calculation:

public static boolean isPrime(long num) {
    return num > 1 && LongStream.rangeClosed(2, (long)Math.sqrt(num)).noneMatch(div -> num % div == 0);
}

public static boolean isPrime1(long num) {
    for (long i = 2, sqrt = (long)Math.sqrt(num); i <= sqrt; i++)
        if (num % i == 0)
            return false;
    return true;
}

Main performance trick is enough to check first Math.sqrt(num) numbers only.

edited Dec 23 '17 at 13:44

answered Dec 23 '17 at 10:21

Oleg Cherednik

17,377
4
21
35

Pretty cool.Thank you.I searched for a "loop" type source code.Thank you. – K.Anuradha Dec 23 '17 at 13:42

score 0 · Answer 5 · answered Dec 23 '17 at 11:09

public static void main(String args[]){
            boolean flag=false;
            int i=1;
            while(i<=100){
                for(int j=2;j<=i/2;j++) {
                    if(i%j==0){
                        flag=true;
                        break;
                    }else {
                        flag=false;
                    }

                }
                 if(flag!=true) {
                        System.out.println("Prime number--->" +i);
                    }
                 i++;
            }

        }

How to solve error java.lang.ArithmeticException when finding prime numbers 1 to 100

5 Answers5