import java.util.Collections;
import java.util.Enumeration;
import java.util.Properties;
import java.util.Vector;

public class SortedProperties extends Properties {
  /**
   * Overrides, called by the store method.
   */
  @SuppressWarnings("unchecked")
  public synchronized Enumeration keys() {
     Enumeration keysEnum = super.keys();
     Vector keyList = new Vector();
     while(keysEnum.hasMoreElements()){
       keyList.add(keysEnum.nextElement());
     }
     Collections.sort(keyList);
     return keyList.elements();
  }
  
  /**
   * Demo
   */
  public static void main(String[] args) throws Exception {
    // regular Properties
    Properties p = new Properties();
    p.put("B", "value B");
    p.put("C", "value C");
    p.put("A", "value A");
    p.put("D", "value D");
    java.io.FileOutputStream fos = new java.io.FileOutputStream("/temp/p.props");
    p.store(fos, "regular props");
    /*
      #regular props
      #Thu Jul 31 22:21:51 EDT 2008
      A=value A
      D=value D
      C=value C
      B=value B
    */
    // same data but with sorted Properties
    SortedProperties sp = new SortedProperties();
    sp.put("B", "value B");
    sp.put("C", "value C");
    sp.put("A", "value A");
    sp.put("D", "value D");
    fos = new java.io.FileOutputStream("/temp/sp.props");
    sp.store(fos, "sorted props");
    /*
      #sorted props
      #Thu Jul 31 22:34:06 EDT 2008
      A=value A
      B=value B
      C=value C
      D=value D
    */
  }
}