How to sort a file

Question

How to sort a file, simple unrefractored example
import java.io.*;
import java.util.*;
public
class Sort
   * Sorts a file that contains data per line using a TreeMap
   * @param args There must be at least one argument, and only the first
   * argument will be interpreted
  public
  static
  void main(String[] args)
  throws Exception
    TreeSet set; // used to sort the data
    BufferedReader buffer; // reads from File with name of args[0]
    PrintWriter writer; // writes to File with the name of args[0].sorted
    String line; // buffer for line read
    set = new TreeSet();
    buffer = new BufferedReader(new InputStreamReader(new FileInputStream(args[0])));
    while ((line=buffer.readLine())!=null) set.add(line.trim());
    buffer.close();
    writer = new PrintWriter(new PrintStream(new FileOutputStream(args[0]+".sorted")));
    for (Iterator i = set.iterator(); i.hasNext(); writer.println(i.next()));
    writer.close();

Answer 1

and here is the clean version as a handy static utility method:
      * Sort lines in a text file in alphabetical order.
      * @param sourceFile File to sort.
      * @param destinationFile File to write sorted content to.
      * @throws IOException If error occured.
     public static void sortFile(File sourceFile, File destinationFile) throws IOException {
        if (sourceFile != null) {
            BufferedReader br = null;
            PrintWriter pw = null;
            TreeSet treeSet = new TreeSet(); //used to sort the data
            try {
                String line = null;
                //read source file into treeSet:
                br = new BufferedReader(new InputStreamReader(new FileInputStream(sourceFile)));
                while ((line = br.readLine())!=null) {
                    treeSet.add(line.trim());
                //write content of treeSet to destination file:
                pw = new PrintWriter(new PrintStream(new FileOutputStream(destinationFile)));
                Iterator iterator = treeSet.iterator();
                while (iterator.hasNext()) {
                    pw.println(iterator.next());
            } finally {
                if (br != null) {
                    br.close();
                if (pw != null) {
                    pw.close();
        }//else: sourceFile unavailbel
    }//sortFile()