Got the break statement to work, but can't figure out the java for condition

Question

I'm trying to figure out how to do the primes from 1 to 101. I've got this so far:

public class BreakShow{
  public static void main(String[] args){
  int i;
  int prime;

  System.out.println("Prime numbers from 1 to 101 : ");
    for (i = 1;i < 102;i++ ){
        for (prime = 2;prime < i;prime++ ){
            if(i % prime == 0) {
                break;
            }
        }
        if(i == prime) {
            System.out.print("  " + i);
        }
    }
  }
}

I can't get it to print the 1. I've tried changing the values for i and prime around, but it doesn't work. Seems to be linked with the print and it's just not continuing. I guess I don't really understand the conditions of the for statement and how it operates.

Answer 1

What's happening is that when i is = 1 (when you're testing for the case of 1), this loop:

for (prime = 2;prime < i;prime++ ){
    if(i % prime == 0) {
        break;
    }
}

Never runs, because prime is never actually less than i, because prime starts at 2. Which means it then checks if i == prime, which it will never be, since prime = 2.

Answer 2

prime variable is initialized with value 2 but you are checking 1==2.

you can test value i and prime before if condition

System.out.println("i:: "+ i+ "  prime:: "+prime);
    if(i == prime) 
        {
            System.out.print("  " + i);
        }

so if clause  does not meet the condition 

Answer 3

Java knows that 1 is not a prime and doesn't print it.

First two google results for 'is 1 a prime number' prove it.

Answer 4

If you are trying to do fizz buzz with prime, then you should only need one loop and mod by 2. You could just do something like this.

for(int i = 1; i <= 101; i++){
   if( (i%2) != 0) // use the smallest even number to check against.
      println("prime");
}

Answer 5

Since second for loop starts with 2, its skipping 1 because of i==prime condition before print. If you really want to print 1, Please update your conditions as below:

     public static void main(String[] args) {
          int prime;
          System.out.println("Prime numbers from 1 to 101 : ");
            for (int i = 1;i < 102;i++ ){
                for (prime= i-2;prime > 1;prime-- ){
                    if(prime< 0 || i % prime == 0) {
                        break;
                    }
                }
                if(prime < 0 || prime==1) {
                    System.out.print("  " + i);
                }
           }
      }