Keeron - 6 months ago 42

Java Question

I am trying to write a program that will list out the prime numbers up to, but not including a number determined by the user.

I want the primes to be separated by commas, but I can't seem to get rid of the comma after the final prime.

Say the user picks the number 10.

The list should be:

2,3,5,7

What I get is:

2,3,5,7,

I know this probably gets asked a lot, but I can't find anything that will help, or that I understand how to apply to my problem.

Could someone point me in the right direction?

Thanks.

`Scanner scanner = new Scanner(System.in);`

int i = 0;

int num = 0;

String primeNumbers = "";

System.out.println("Pick a number, any number: ");

int n = scanner.nextInt();

for (i = 1; i < n; i++) {

int counter = 0;

for (num = i; num >= 1; num--) {

if (i % num == 0) {

counter = counter + 1;

}

}

if (counter == 2) {

primeNumbers = primeNumbers + i + ",";

}

}

System.out.println("\nThe prime numbers up to " + n + " are: ");

System.out.println(primeNumbers);

Answer

Rewrite

```
primeNumbers = primeNumbers + i + ",";
```

in the following way

```
if(!primeNumbers.isEmpty()) {primeNumbers+=".";}
primeNumbers = primeNumbers + i;
```