// Using try/catch to recover from a bad command-line parameter.

    private void parseCommands () {

        boolean fileFound = false;

        //  Second pass: look for source file names.

        for (int i = 0; i < argv.length; i = i + 1) {
            if (argv[i] != null) {
                String src = argv[i];
                int n = src.length();
                if ((n > 2) && src.substring (n - 2, n) . equals (".q")) {
                    fileFound = true;
                    try {
                        String dst = src.substring (0, n - 1) . concat ("lap");
                        FileInputStream fin = new FileInputStream (src);
                        FileOutputStream fout = new FileOutputStream (dst);
                        compileFile (fin, fout);
                    }
                    catch (FileNotFoundException e) {
                        System.err.println (src + " not found.");
                    }
                } else
                System.err.println ("Ignoring command-line argument: "
                                    + argv[i]);
            }
        }
        if (! fileFound)
            compileStandardInput ();
    }