Help with PrimeDirective.Java

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1

If someone can help. Trying to complete the PrimeDirective.Java challenge.

https://www.codecademy.com/courses/learn-java/projects/java-prime-directive

My code is not returning the prime numbers but the original True/False statements. I have looked through many of the help queries and cannot see an answer to
this. Returns 4 errors when checked.

// Import statement:
import java.util.ArrayList;

class PrimeDirective {
  
  // Add your methods here:
  public boolean isPrime(int number) {
  
  if (number == 2) {
    return true;
   } 
   else if (number < 2) {
     return false;
   }
  
  for (int i = 2; i < number; i++) {
    if (number % i == 0) {
      return false;
      } 
      }
        return true;
     
  }
  public ArrayList<Integer> onlyPrimes(int[] numbers) {
    ArrayList<Integer> primes = new Arraylist<Integer>();
    
    for (int number : numbers) {
      if (isPrime(number)) {
        primes.add(number);
        }
    }
    return primes;
  }
}
    public static void main(String[] args) {

    PrimeDirective pd = new PrimeDirective();
    int[] numbers = {6, 29, 28, 33, 11, 100, 101, 43, 89};
    /*
    System.out.println(pd.isPrime(7));
    System.out.println(pd.isPrime(28));
    System.out.println(pd.isPrime(2));
    System.out.println(pd.isPrime(0))
   */
   System.out.println(pd.onlyPrimes(numbers));

    
  }

Thanks

2

You have a } in the wrong place.

The last } before the main method should be after the main method.

details 
// Import statement:
import java.util.ArrayList;

class PrimeDirective {
  
  // Add your methods here:
  public boolean isPrime(int number) {
  
  if (number == 2) {
    return true;
   } 
   else if (number < 2) {
     return false;
   }
  
  for (int i = 2; i < number; i++) {
    if (number % i == 0) {
      return false;
      } 
      }
        return true;
     
  }
  public ArrayList<Integer> onlyPrimes(int[] numbers) {
    ArrayList<Integer> primes = new ArrayList<Integer>();
    
    for (int number : numbers) {
      if (isPrime(number)) {
        primes.add(number);
        }
    }
    return primes;
  }
} // <= This } does not belong here
    public static void main(String[] args) {

    PrimeDirective pd = new PrimeDirective();
    int[] numbers = {6, 29, 28, 33, 11, 100, 101, 43, 89};
    /*
    System.out.println(pd.isPrime(7));
    System.out.println(pd.isPrime(28));
    System.out.println(pd.isPrime(2));
    System.out.println(pd.isPrime(0))
   */
   System.out.println(pd.onlyPrimes(numbers));

    
  }
// <= There should be a } here to end the class
2 Likes
3

Also,

// You wrote:
ArrayList<Integer> primes = new Arraylist<Integer>();

// It should be:
ArrayList<Integer> primes = new ArrayList<Integer>();
1 Like
4

Thanks for replying. I can’t see any difference between the two lines of code. What has changed?

5

OK, thanks. Moved that, same issue

6

You wrote Arraylist instead of ArrayList

7

Can’t seem to get it to work still, just returns the true/false etc.

// Import statement:
import java.util.ArrayList;

class PrimeDirective {

// Add your methods here:
public boolean isPrime(int number) {

if (number == 2) {
return true;
}
else if (number < 2) {
return false;
}

for (int i = 2; i < number; i++) {
if (number % i == 0) {
return false;
}
}
return true;

}
public ArrayList onlyPrimes(int numbers) {
ArrayList primes = new ArrayList();

for (int number : numbers) {
  if (isPrime(number)) {
    primes.add(number);
    }
}
return primes;

}

public static void main(String[] args) {

PrimeDirective pd = new PrimeDirective();
int[] numbers = {6, 29, 28, 33, 11, 100, 101, 43, 89};
/*
System.out.println(pd.isPrime(7));
System.out.println(pd.isPrime(28));
System.out.println(pd.isPrime(2));
System.out.println(pd.isPrime(0))

*/
System.out.println(pd.onlyPrimes(numbers));

}
}Preformatted text

8

Ah, it’s working now. Thanks all

1 Like