import java.io.FileWriter;
import java.nio.charset.Charset;
import java.util.Scanner;

public class App {
    public static void main(String[] args) 
            throws Exception {
        
        String os = System.getProperty("os.name").toLowerCase();
        String charsetName = "utf-8";

        if(os.contains("win")) {
            charsetName = "cp1250";
        }

        Scanner sc = new Scanner(System.in, charsetName);
        System.out.print("Név: ");
        String name = sc.nextLine();
        sc.close();

        // A FileWriter() ilyen konstruktora 11 Java verziótól elérhető:
        FileWriter fw = new FileWriter("adat.txt", 
            Charset.forName("utf-8"), true);
        fw.write(name);
        fw.write("\n");
        fw.close();
        
    }
}