Борьба с FileWriter

package player;
 
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
 
public class mp3player {
    
    private String uni_id;
    private int capacity;
    private String name;
    private boolean headphones;
    private static int next_id = 1;
    
    public mp3player(){
        uni_id = "PlayerID" + next_id++;
    }
 
    public static void main(String[] args) {
        
        
        mp3player mp3_1 = new mp3player();
        mp3player mp3_2 = new mp3player();
        
        ArrayList<mp3player> players = new ArrayList<mp3player>();
        players.add(mp3_1);
        players.add(mp3_2);
        
        File f = new File("C://SomeDir/notes3.txt");
        
        try {
            FileWriter writer = new FileWriter(f);
            for(mp3player m : players){
                writer.write(m.uni_id);
                writer.write("\n");
            }
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
}

                writer.write(System.lineSeparator());

    PrintWriter writer = new PrintWriter ("file.txt");
    writer.println ("hello");
    writer.close ();