Why this code don't work on CodeEval?

Question

So, code below, that takes serial numbers as arguments from txt file, works correctly on my computer. Every number is written on one line. So, here is the code:

import java.io.*;
import java.util.*;
import javax.swing.JOptionPane;

public class Main {
    public static int fiboComputingAct(int serial){
        if (serial == 1 || serial == 2) {
            return 1;
        }else{
            int nMinus2 = 1;
            int nMinus1 = 1;
            int result = 0;
            for (int i = 3; i <= serial; i++){
                result = nMinus1 + nMinus2;
                nMinus2 = nMinus1;
                nMinus1 = result;   
            }
            return result;
        }   
    }

    public static void main (String [] args){
        try {
            File textFile = new File("texts/1.txt"); //"texts/1.txt" will be replaced on args[0] in codeeval
            Scanner scan = new Scanner(textFile);
            int fiboSerialNumber;
            while (scan.hasNextLine()) {
                fiboSerialNumber = scan.nextInt();
              System.out.println(fiboComputingAct(fiboSerialNumber));
                }
            } catch (Exception e) {JOptionPane.showMessageDialog(null, "File is not found");}   
        }   
    }

But it doesn't work in CodeEval. That's what the site compiler say:

Fontconfig error: Cannot load default config file Exception in thread "main" java.awt.HeadlessException: No X11 DISPLAY variable was set, but this program performed an operation which requires it. at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:207) at java.awt.Window.(Window.java:535) at java.awt.Frame.(Frame.java:420) at java.awt.Frame.(Frame.java:385) at javax.swing.SwingUtilities$SharedOwnerFrame.(SwingUtilities.java:1759) at javax.swing.SwingUtilities.getSharedOwnerFrame(SwingUtilities.java:1834) at javax.swing.JOptionPane.getRootFrame(JOptionPane.java:1697) at javax.swing.JOptionPane.showOptionDialog(JOptionPane.java:863) at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:667) at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:638) at javax.swing.JOptionPane.showMessageDialog(JOptionPane.java:609) at Main.main(Main.java:45)

So it looks like CodeEval doesn't give you a GUI to put your error messages on. Instead of popping up a `JOptionPane` when you get an exception, just `e.printStackTrace()` instead. — azurefrog, Feb 17 '15 at 01:32

score 0 · Accepted Answer · edited May 23 '17 at 12:06

According to the stack trace, the error is occurring here:

JOptionPane.showMessageDialog(null, "File is not found");

Taking a look at the documentation for the HeadlessException, we see that it is:

Thrown when code that is dependent on a keyboard, display, or mouse is called in an environment that does not support a keyboard, display, or mouse.

A bit more research makes me believe that CodeEval is probably trying to execute your code in a headless linux environment.

To avoid this error, just replace the graphical error reporting with a simple e.printStackTrace() in your catch block.

Why this code don't work on CodeEval?

1 Answers1