Stuff

/*
pa3
Colin Ahern
cahern
program that takes a list of input from a file and determines primality
*/

import java.io.*;
import java.util.Scanner;

class Primes{
   public static void main(String[] args){
      Scanner sc;
      int number,temp=-1,testr;
      if(args.length==0){
         Usage();
         return;
      }
      for(int i=0;i<args.length;i++){
         try{
            sc = new Scanner(new File(args[i]));
         }catch(FileNotFoundException e){
            Usage();
            continue;
         }
         while(sc.hasNextLine()){
            while(temp<=0){
               if(sc.hasNextInt()){
                  temp=sc.nextInt();
               }else{
                  sc.next();
               }
            }
            number=temp;
            testr=testPrime(number);
            if(testr==1) System.out.println(number+" is prime.");
            if(testr>1) System.out.println(number+" is divisable by "+testr);
            if(testr==0) System.out.println("1 is neither prime nor composite");
            temp=-1;
         }
      }
   }

static int testPrime(int n){
   int temp;
   if(n==1) return 0;
   for(int i=2;i*i<=n;i++){
      temp=n%i;
      if(temp==0){
         return i;
      }
   }
   return 1;
}
static void Usage(){
   System.out.println("Usage: java Primes input_file");
}
}