My USACO Solutions: Your Ride is Here

I decided to do the USACO training program over the summer. Meanwhile, the darn program has all their solutions/analysis in C++, which I don't do... so I'm posting my solutions here for 1. Just for the heck of it and 2. So other people can tell me what I can do better

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

public class ride 
{
 public static void main(String [] args) throws IOException {
  
     BufferedReader f = new BufferedReader(new FileReader("ride.in"));
     PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("ride.out")));
    
     String comet = f.readLine();
     String group = f.readLine();
  
  //I didn't know if java has the ord() or char() function like python does
  //and I'm too lazy to find out. Besides, this is easier to understand
     String[] list_alpha = {"A","B","C","D","E","F","G","H","I","J","K","L",
   "M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
     ArrayList list = new ArrayList(Arrays.asList(list_alpha));
     
     int comet_num=1;
     int group_num=1;
     
  //At the time of submission, I split the loop to two for loops... >.>
  //didn't realize that they were same length
     for (int x = 0 ; x < comet.length() ; x++)
     {
      comet_num *= list.indexOf((comet.substring(x, x+1)))+1;
   group_num *= list.indexOf((group.substring(x, x+1)))+1;
     }
     
     if ((comet_num % 47) == (group_num % 47)){
      out.println("GO");
     }
     
     else out.println("STAY");
     
     out.close();
     System.exit(0);
 }
}

-runiteking1 Got comments? Post them below!