CIS 260 SimpleFileIO.java

Code

/*
    SimpleFileIO.java
    David Klick
    2009-01-20
    CIS 260
    
    This program reads in integers from a file and writes
    the prime numbers it reads to another file.
*/

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.PrintWriter;
import java.util.Scanner;

public class SimpleFileIO {
    public static void main(String[] args) throws FileNotFoundException {
        Scanner in = new Scanner(new FileReader("int1to100.txt"));
        PrintWriter out = new PrintWriter("primes1to100.txt");
        int count = 0;
      
        while (in.hasNextInt()) {
            int i = in.nextInt();
            if (isPrime(i)) {
                count++;
                out.println(i);
            }
        }
        in.close();
        out.close();
        System.out.println(count + " primes were found.");
    }
   
    private static boolean isPrime(int n) {
        if (n < 2) return false;
        int limit = (int) Math.sqrt(n);
        for (int i=2; i<=limit; i++) {
            if (n % i == 0) return false;
        }
        return true;
    }
}