public static void main(String[] args) throws Exception
    {
        Map<String,Integer> map = new HashMap<String,Integer>();
        searchFile(map,new File("e:"));
        
        Set set = map.entrySet();
        for(Iterator i = set.iterator();i.hasNext();)
        {
            Map.Entry<String, Integer> temp = (Map.Entry<String, Integer>)i.next();
            System.out.println(temp.getKey() + ":" + temp.getValue());
        }
    }
    public static void searchFile(Map map,File file) throws Exception
    {
        if(file.isFile())
        {
            if(file.getName().lastIndexOf(".") != -1)
            {
                String fileName = file.getName().toLowerCase();
                String suffix = fileName.substring(fileName.lastIndexOf(".")+1,fileName.length());
                if(map.containsKey(suffix))
                {
                    map.put(suffix, Integer.parseInt(map.get(suffix).toString()) + 1);
                }
                else
                {
                    map.put(suffix, 1);
                }
            }
            
        }
        else
        {
            File[] files = file.listFiles();
            for(File tempFile:files)
            {
                searchFile(map,tempFile);
            }
        }
    }