sorting

[Donald Wynn]

I want to sort a some report totals thats in a hashtable whats the best way to do this?

[Sumeet Gaikwad]

Dear Donald,
If you want to sort the hashtable then use the following code.

 sorting by key & retriving an element:-
 
 for sorting --
 
     public List sortHashKeys(Hashtable hash){
        List l = new ArrayList();
        Enumeration enum = hash.keys();
        while(enum.hasMoreElements()){
           l.add(enum.nextElement());
      }
      Collections.sort(l);
      Collections.reverse(l);
      return l;
    }
 
 
 for retriving --
 
    Use 'iterator' or 'listiterator' or 'for-loop'. 
 
sorting by value & retriving an element:-
 
 for sorting -- 
 
     public List sortHashValues(Hashtable hash){
        Map m = hash;
        List l = new ArrayList(m.values());
        Collections.sort(l);
        Collections.reverse(l);
        return l;
    }
 
 for retriving --
 
    Use 'iterator' or 'listiterator' or 'for-loop'. 
 
sorting by value & retriving a key-value pair:-
 
 for sorting -- 
 
     public Map.Entry [] sortTotalHash(Hashtable hash){
        Set set = hash.entrySet();
        Map.Entry [] entries = (Map.Entry [])set.toArray(new Map.Entry[set.size()]);
 
        Arrays.sort(entries, new Comparator(){
             public int compare(Object o1, Object o2){
                Integer v1 = Integer.valueOf((String)((Map.Entry)o1).getValue());
                Integer v2 = Integer.valueOf((String)((Map.Entry)o2).getValue());
                return ((Comparable)v2).compareTo(v1); 
                // swapping v1 & v2  shall reverse the sorting order.
             }
      }); 
            return entries;
     }
 
 Note :
 Here my hashtable contains 'key' & 'value', both of type 'String'. 
 But for comparison, I have taken the values to 'Integer' form.
 You can reform the objects to any required type, for comparison.  
 
 for retriving --
 
     for(int i=0; i<entries.length; i++) {
          String key = (String)entries[i].getKey(); // get Key
        String value = (String)entries[i].getValue(); // get Value 
     }
 
  

Hope this helps you.