Hash Table - Sorting

[Vishnu Prakash]

Hi

I had created a HashTable instance with entries in it. I know HashTable class doesn't support sorting. But I need the key/value to be sorted in someway. TreeMap class supports sorting. But I don't know how to use it. Please help to sort the entries.

  
public class Vishnu {
staticVishnu cd;
public static void main(String[] args) {
cd = new Vishnu();
cd.getHashValues( );
}
        public  void getHashValues( ) {
Hashtable rt = test();
Enumeration enum1 = rt.keys();
Enumeration enum2 = rt.elements();
 
while (enum2.hasMoreElements() && enum1.hasMoreElements()) {
System.out.println("\n"+enum1.nextElement() + ": " + enum2.nextElement());
}
}
 
                public Hashtable test() {
                        Hashtable hash = new Hashtable();
Vector v1 = cd.getJavaVector();
Vector v2 = cd.MicrosoftVector();
hash.put("Java",v1);
        return hash;
}
             public Vector getJavaVector() {
             Vector java =new Vector();
             java.addElement("Core_Java");
             java.addElement("Servlet");
             java.addElement("JSP");
             java.addElement("Web_services");
             java.addElement("XML");
             return java;
}
 
                      public Vector getMicrosoftVector() {
Vector microsoft=new Vector();
microsoft.addElement("Visual_Basic");
microsoft.addElement("ASP");
microsoft.addElement("Dot_Net");
microsoft.addElement("VC++");
microsoft.addElement("VCStudio");
return microsoft;
}
}

[Paul Sturrock]

TreeMaps sort entries by key, based on the "natural order" of the key. What that means is that whatever object you use as a key must implement the Comparable interface. This is an interface which defines the compareTo(Object o) method, so the implementing object will have to implement how you decide one object needs order after another.

The easiest way to use a TreeMap is to use a Key which already implements Comparable - Strings, Integers, Longs etc. are the most obvious. Assuming you do this, you know that as you put object into the TreeMap, they are ordered as defined by the key's natural order.
[ March 01, 2005: Message edited by: Paul Sturrock ]