Sorting a HashTable by the values (including alphanumeric)

I have a HashTable with alphanumeric values. 开发者_如何学编程I want to sort them.

How can I achieve it?

HashTable doesn't preserve the order.

So better Create a List out of it and Sort it.

You need to wrap your types into a class and then implement a Comparator that compares all the types of values (in your term),

class Foo implements Comparator<Foo>{
  private int no;
  private String alpha;
  //+getter/setters

  public int compare(Foo f1, Foo f2){
      //put your logic here
  }
}

Why? You presumably chose HashTable over TreeMap because it had better performance (and no ordering). If you don't want the performance and you do want the ordering, use a TreeMap.

If you don't want to create a new class to hold the key/value relationship and it you are not interested in a TreeMap, then something like the following will also work:

ArrayList<Entry<String,String>> list = new ArrayList<Entry<String,String>>();
list.addAll(map.entrySet());

Collections.sort(list, new Comparator<Entry<String,String>>() {

    @Override
    public int compare(Entry<String, String> o1, Entry<String, String> o2) {
        //your logic here;
    }

});

First question - do you really mean sort the values, or do you mean sort the keys?

If you only want to access the sorted values in order once the best way is create a list or array then sort.

For values: Arrays.sort(table.values().toArray()) or Collections.sort(new ArrayList(table.values()))

For keys: Arrays.sort(table.keySet().toArray()) or Collections.sort(new ArrayList(table.keySet()))

For more on these sorting methods: Arrays.sort() or Collections.sort().

If you want to repeatedly use based on sorted keys, you would be better using a TreeMap.

If you repeatedly want to access based on sorted values (rather than keys), then you could always insert in order into a LinkedHashMap, which will keep the ordering.