How to store data in the text line by line?

Question

when i write the data into *.txt, the data I wrote before is deleted.
how can wrote the data into the txt following the existing data?
how to write data line by line? many thanks!
my code is like:
private String text = "i am yanbo du, i am a boy.";
public BufferWriteMultiKey( ) {         
     try {
          StringTokenizer st = new StringTokenizer(text, " ,.");
          File fil =new File("f.txt");
     //FileWriter fw = new FileWriter(fil);
     //BufferedWriter bw= new BufferedWriter(fw);
     DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(fil)));
while(st.hasMoreTokens())
String s = st.nextToken();
     //bw.newLine();
     out.writeChars(s);
out.writeChars("\n");
out.close();

Answer 1

use a random access file and append text at the end.
read the file in line by line using a BufferedReader and store each line in a List of Strings, of course.
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