Java Prime Number help

[wolf2009]

I need help with making this prime number generator in java for univ HW. I'm using BlueJ for writing and testing the code.

I have made the code, but some logic is wrong. The user has to enter the starting number, 2 for HW, and the ending number. Then the code should display all the prime numbers between the two numbers. And it has to be done with loops and if-else statements.

import java.util.Scanner;
public class PrimeNumber
{
    public static void main(String [] args)
    {
        int num1, num2, count, i = 2, prChk = 0 , m = 0;
        Scanner keyIn = new Scanner (System.in);
    
      
        System.out.print("Enter First number : ");
        num1 = keyIn.nextInt();
        
        System.out.print("Enter Second number : ");
        num2 = keyIn.nextInt();
        
        count = num1;
              
        while(count <= num2)
        {
            while(i < count)
            {
                prChk = count % i;
                if(prChk == 0)
                    m = 0;
                else if(prChk == 1)
                    m = 1;
                i++;
            }
            if (m == 0)
                System.out.println(count + ": prime");
            else if(m ==1)
                System.out.println(count + ": not prime");
            count++;
        }
    }
}

What am I doing wrong ?

 

[BillLeeLee]

What's happening in the code that makes you think it's wrong? What's it outputting?

Also, you never reinitialize i.

 

[Snowknight26]

An exception will be thrown if someone types anything other than an int.

 

[generelz]

launch your program in a debugger; you'll quickly see where you're going wrong.

 

[the_transporter]

edit: nm

 

[LuminaryJanitor]

... I'm using BlueJ ...

Don't. BlueJ is garbage. Go get Eclipse.

 

[FireStormGS]

Is eclipse better than what sun offers on their site, netbeans?

 

[KaosDG]

Is eclipse better than what sun offers on their site, netbeans?

It's debatable, and some people get their panties in a bunch over it...

It's like emacs vs. vi, Mac vs. Windows, etc.. mainly preference.

Netbeans is very good, and I like it because of the swing GUI tools (helps with quick GUI prototyping).

I personally use Eclipse more though, I just find it more extensible and flexible for my needs. (Plus I can run it from a flash drive without it wigging out on me)

 

[devman]

Is eclipse better than what sun offers on their site, netbeans?

Having used both I find Eclipse is more flexible when it comes to working with Java EE, although that can depend on implementations (i.e. Glassfish). For straight Java SE code its pretty much a dead heat however if your making heavy use of Swing, Netbeans takes an advantage if you like visual coding.

I also find Eclipse is a lot easier to use when you are working on a team with other people who use different (or don't use) IDEs.

It really does boil down to Vim vs. Emacs type debate but I find that one or the other is usually better at accomplishing some goal so it really depends on the project/module your working on.

 

[wolf2009]

Don't. BlueJ is garbage. Go get Eclipse.

i'm a beginner and they are teaching with BlueJ in univ. but i'll move on to something else later as you said. I'll give eclipse a try later on

 

[Dangman]

What's happening in the code that makes you think it's wrong? What's it outputting?

+ 1 to this question. I'm running the code now. Doesn't seem to be anything wrong to me. Unless there's a set of criteria I'm missing?