CODEWITHSUNDEEP
javalines
bergh070
bergh070

Reputation: 11

to many new lines and weird distribution in Java

i am writing a program that checks for prime numbers and then displays the first 1000 in rows of 10. The program works fine except for the fact that when i display them at random there are new lines. The first three lines are printed correctly but after that it goes haywire. Can someone please help? Much appreciated.

public class PrimeTest{
public static void main(String[] args){

boolean prime;
int primeCount = 0;

//For loop to increase the integer that is checked by one and print if prime

for (int i = 2; primeCount != 1000; i++){
    prime = isPrime(i);     
    if (prime == true){
       primeCount++;
       System.out.print(i + " ");}
    else if (primeCount % 10 == 0){
       System.out.print("\n");}             
    else ;}
    } 

// Method to check number for Primeness
public static boolean isPrime(int i){
    boolean check = true;
            for (int n = 2; n < i; n++){
        if (i % n != 0){
            check = true;}
        else if ( i % n == 0){ 
            check = false; break;}
    } return check;

}
}

This is (a part of) the output i get: 

2 3 5 7 11 13 17 19 23 29 
31 37 41 43 47 53 59 61 67 71 
73 79 83 89 97 101 103 107 109 113 












127 131 137 139 149 151 157 163 167 173 




179 181 191 193 197 199 211 223 227 229 


233 239 241 251 257 263 269 271 277 281 
283 293 307 311 313 317 331 337 347 349 


353 359 367 373 379 383 389 397 401 409 








419 421 431 433 439 443 449 457 461 463 


467 479 487 491 499 503 509 521 523 541 




547 557 563 569 571 577 587 593 599 601 




607 613 617 619 631 641 643 647 653 659 
661 673 677 683 691 701 709 719 727 733 




739 743 751 757 761 769 773 787 797 809 
811 821 823 827 829 839 853 857 859 863

Upvotes: 0

Views: 65

Answers (5)

bergh070
bergh070

Reputation: 11

Thanks a lot for the swift response guys, i really appreciate it! After implementing your suggestions i got it to work perfectly :D

This is the code i ended up using:

public class PrimeTest{
public static void main(String[] args){

boolean prime;
int primeCount = 1;

//For loop to increase the integer that is checked by one and print if prime

for (int i = 2; primeCount != 1000; i++){
prime = isPrime(i);     
if (prime == true){
   primeCount++;
   System.out.print(i + " ");}
   if (primeCount % 11 == 0){
   System.out.print("\n");
primeCount = primeCount + 1;}             
else ;}
} 

// Method to check number for Primeness
public static boolean isPrime(int i){
boolean check = true;
        for (int n = 2; n < i; n++){
    if (i % n != 0){
        check = true;}
    else if ( i % n == 0){ 
        check = false; break;}
} return check;

}
}

Upvotes: 0

Stephen C
Stephen C

Reputation: 719679

The problem is in the logic that decides when to output a newline. You are currently testing to see if a newline should be output after every non-prime by testing the prime count. That works if there is only one non-prime after the last prime on a line. But if there are multiple non-primes, you output a newline for each one.

Obviously, the prime count only changes when you have just found a prime. So you need to decide to output a newline immediately after (or before) you output a prime.

Upvotes: 1

Artur Peniche
Artur Peniche

Reputation: 479

Because if you get stuck with your prime counter at some number divisible by 10 (30 in the first example), you will spam \n you need to change this else statement

else if (primeCount % 10 == 0){
       System.out.print("\n");}

to this

for (int i = 2; primeCount != 1000; i++){
    prime = isPrime(i);     
    if (prime == true){
       primeCount++;
       System.out.print(i + " ");
       if (primeCount % 10 == 0){
          System.out.println();              
        }
    } 
}

Upvotes: 1

J Atkin
J Atkin

Reputation: 3150

Your problem is hiding right here:

if (prime == true){
   primeCount++;
   System.out.print(i + " ");}
else if (primeCount % 10 == 0){
   System.out.print("\n");}             
else ;}

What's happening is when your prime count is a multiple of 10 and you are waiting for a new prime, the else if is running and you are getting incorrect newlines.

Upvotes: 0

locoyou
locoyou

Reputation: 1697

The if statement is wrong. It should be:

if (prime == true){
   primeCount++;
   System.out.print(i + " ");
   if (primeCount % 10 == 0){
      System.out.print("\n");
   }
}

In your code, a "\n" will be printed every time there is a non-prime number when primeCount % 10 == 0.

Upvotes: 3

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