Thread: please help me with the Code below

Hello guys,

I have got a task to print all prime numbers in a certain range. Could you please tell me why the code does not work? The data validation works correct but the main task to print the prime numbers does not. Thank you.

import java.io.*;
 
public class Prime {
 
	BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
 
	public static int lowerBound;
	public static int higherBound;
 
	public void getInput() throws IOException
	{
		String line1 = input.readLine();
		String line2 = input.readLine();
		int lowInput = Integer.parseInt(line1);
		int highInput = Integer.parseInt(line2);		
		lowerBound = lowInput;
		higherBound= highInput;
 
	}
 
 
	public void validatedata() throws IOException
	{
 
	do{
	    if (higherBound <= lowerBound)
	    {
	    	System.out.println("The upper bound should be at least as big as the lower bound. " + "Please try again");
	        getInput();
	    }     
          else 
    	     System.out.println("the lower bount is: " + lowerBound);
		     System.out.println("the high bound is: " + higherBound);
      } while (higherBound <= lowerBound);
	}	
 
	public void prime_calculation() throws IOException
	{
 
		while (lowerBound > 2)
		{
			int k = 0;
			for (k = lowerBound; k <= higherBound; k++)
			{
			  if ((higherBound % k) != 0)
			  {
			    System.out.println(k);
			    getInput();
			  }
			}	  
		}
	}
 
}

User class:

import java.io.*;
 
public class PrimeUser extends Prime {
 
 
	public static void main(String argv[]) throws IOException
	{
 
		Prime isprime = new Prime();
		isprime.getInput();
		if (lowerBound < 2)
			System.out.println("You typed in number less than two. Please try again.");
		else if (higherBound <= lowerBound)
			isprime.validatedata();
		else
			isprime.prime_calculation();
	}
 
 
 
}

If I type in:

lower bound = 1
upper bound = 5

Output - "You typed in number less than two. Please try again." ---- This works fine

2)
lower bound = 6
upper bound = 3

Output - "The upper bound should be at least as big as the lower bound." - Works fine

3)
lower bound = 2
upper bound = 100

Output - nothing ----- doesn't work fine

The output should be - 2, 3, 5, 7 etc. In other words it should list all prime numbers

Giving the user a blank screen and expecting him/her to know what to do with it is unfriendly and unreasonable. Improve your prompts so that the user knows what to do.

Adding prompts may also show you what the program is doing, allowing you to see where you're making logic errors.

Will do. Thanks. However, this does not solve my problem as main code does not work.

I am looking for someone to tell me the solution as I cannot fix it.

At least you're honest. We're trying to give you basic debugging techniques that should help you find the source of the problem(s) and then fix them with or without our help. You can travel down that path with us, or you can move on. We're not simply going to fix it for you.

Ok guys,

I fixed it and found my error. Please see below. I used boolean true/false for the purpose. However, now I am struggling with another requirement. I want a message to be printed if there are no prime numbers in the range at all. I just want a single message " No primes found". Can you please help me?

This is my main method:

 	public void prime_calculation() throws IOException
	{	
 
		while ((lowerBound >= 2) && (higherBound > lowerBound))
		{
			for (int k = lowerBound; k < higherBound; k++)
			{
				boolean primecheck = true;
 
					for (int j=2; j < k; j++)
					{
						if (k % j == 0)
						{
							primecheck = false;
						     break;
						}
					}
				if (primecheck)
					System.out.println(k);
			}
		validatedata();
		}	
	}

if ( noPrimesFound )
{
    System.out.println( "No primes found in the specified range." );
}

Yes I know that. Already tried it before. However, the issue comes from the fact that it is posted more than once. I want a single statement if there are no matches. For example in my code it would be:

if (primecheck == false)
 System.out.println("No primes found");

And for example when I input -

lower bound - 2
upper b - 10

It displays
No primes found
No primes found
No primes found