Prime Numbers
Java Code
/** * PrimeNumbersToFile.java * Created by Stijn Strickx on Oct. 7 2005 * Copyright 2005 Stijn Strickx, All rights reserved */ import java.io.*; public class PrimeNumbersToFile{ public static void main(String[] arguments) throws java.io.IOException { int number; long maxnumber = 0; int divider; int breakteller = 0; boolean prime; double rootnumber; maxnumber = getNumber("At which number should the program stop searching for further prime numbers? "); try { FileOutputStream fos = new FileOutputStream("PrimeNumbersFile.txt"); PrintStream ps = new PrintStream(fos); ps.print(2 + " "); for (number = 3; number <= maxnumber; number = number+2){ rootnumber = Math.sqrt(number); prime=true; for (divider = 3; prime && (divider <= rootnumber); divider = divider+2) if((number%divider) == 0) prime = false; else{ prime = true; } if(prime){ breakteller = breakteller+1; ps.print(number + " "); if(breakteller == 20){ ps.println(); breakteller = 0; } } } System.out.print("You can now access the PrimeNumbersFile.txt which is "); System.out.println("in the same directory as the .class file of this program."); ps.close(); } catch (FileNotFoundException e) { System.err.println("error writing to file" + e); } } static long getNumber(String question) throws java.io.IOException { String theNumber; long number = 0; BufferedReader in = new BufferedReader (new InputStreamReader(System.in)); System.out.print(question); theNumber = in.readLine(); System.out.println(); number = Long.parseLong(theNumber); return number; } }