public class Solution() {
    public void writeFile() {
        try {
            tryWriteFile();
        }catch(IOException e) {
            System.err.println("Hiba! A kiírás sikertelen!");
            System.err.println(e.getMessage());    
        }
    }

    public void tryWriteFile() throws IOException {
        try(FileWriter fw = new FileWriter("data.txt", true)){
            fw.write(aside + ":");
            fw.write(bside + ":");
            fw.write(area + "\n");
        }
    }
}