import java.io.*;
 
public class Writing{
    public static void main(String [] args)
    {
    try{
       File file = new File("mytext.txt");
       PrintWriter out =
            new PrintWriter(
                new BufferedWriter(
                    new FileWriter(file, true)));  
                }
                catch (IOException e)
		{
			System.err.println ("Unable to write to file");
			System.exit(-1);
            }
 
        }
    }

import java.io.*;
import java.util.Scanner;
...
try {
  PrintStream ps = new PrintStream(new File("file.txt"));
  Scanner s = new Scanner(System.in);
  String lineBuffer;
 
  lineBuffer = s.nextLine();
 
  ps.println(lineBuffer);
} catch (IOException ioex) {
  ...
} finally {
  ps.close();
  s.close();
}
return;
...