// Marty Stepp, CSE 142, Autumn 2010                                                                        
// This program prints prime numbers up to a given maximum.                                                 
// The purpose of the program is to demonstrate the idea of                                                 
// fencepost problems and fencepost loops.                                                                  

import java.util.*;

public class PrintNumbers {
    public static void main(String[] args) {
        printPrimes(50);
        printNumbers2(5);
        printNumbers2(12);
        printNumbers2(1);
        
    }

    // Prints all prime numbers up to the given max, separated by commas.                                   
    // If the max is less than 2, a blank line of output is produced.                                       
    public static void printPrimes(int max) {
        // post
        System.out.print(2);
        
        for (int i = 3; i <= max; i++) {
            int f = countFactors(i);
            if (f == 2) {
                System.out.print(", " + i);
            }
        }
        System.out.println();
    }
    
    // Returns the number of factors of the given integer.                                                  
    // Assumes that n >= 1.                                                                                 
    public static int countFactors(int n) {
        int count = 0;
        for (int i = 1; i <= n; i++) {
            if (n % i == 0) {
                count++;
            }
        }
        return count;
    }
    
    // Prints all numbers 1-n separated by commas.
    public static void printNumbers(int max) {
        // post
        System.out.print(1);
        
        for (int i = 2; i <= max; i++) {
            System.out.print(", " + i);
        }
        System.out.println();
    }
    
    // Prints all numbers 1-n separated by commas.  (second version)
    public static void printNumbers2(int max) {
        // post
        for (int i = 1; i <= max - 1; i++) {
            System.out.print(i + ", ");
        }
        System.out.println(max);
    }
}