import java.io.*;
import java.text.*;
import java.util.*;

public class LesenSchreibenTextdatei
{
  public static void main( String[] args )
  {
    final String[] KEYS = { "user.name", "user.language", "user.home",
                            "os.name", "java.version" };
    Vector vec = new Vector();
    String s;

    // read the lines to the vector
    try {
      BufferedReader in = new BufferedReader(
                          new InputStreamReader(
                          new FileInputStream( "MeineTextDatei.txt" ) ) );
      while( null != (s = in.readLine()) ) {
        vec.add( s );
      }
    } catch( FileNotFoundException ex ) {
    } catch( Exception ex ) {
      System.out.println( ex );
    } finally {
      if( in != null ) in.close();
    }

    // if the file doesnt exist, create new
    if( 0 >= vec.size() ) {
      for( int i=0; i<KEYS.length; i++ ) {
        vec.add( KEYS[i] + " = " + System.getProperty( KEYS[i] ) );
      }
    }

    // add new entry to the vector
    vec.add( "Zeitstempel = " + new SimpleDateFormat(
                         "yyyy-MM-dd HH:mm:ss,SSS" ).format( new Date() ) );

    // write all elements as line
    try {
      BufferedWriter out = new BufferedWriter(
                           new OutputStreamWriter(
                           new FileOutputStream( "MeineTextDatei.txt" ) ) );
      for( int i=0; i<vec.size(); i++ ) {
        s = vec.get( i ).toString();
        System.out.println( s );
        out.write( s, 0, s.length() );
        out.newLine();
      }
    } catch( IOException ex ) {
      System.out.println( ex );
    } finally {
      if( out != null ) out.close();
    }
  }
}